PDR MEMBER LOGIN:
  • PDR Search

    Required field
  • Advertisement
  • CLASSES

    Biguanide Antidiabetics

    DEA CLASS

    Rx

    DESCRIPTION

    Oral biguanide antidiabetic agent that decreases hepatic glucose production and improves insulin sensitivity
    Used for Type 2 DM as monotherapy or in combination with other drugs including insulin; considered the initial drug of choice for type 2 DM
    Risk of lactic acidosis is low but requires care in prescribing and monitoring

    COMMON BRAND NAMES

    Fortamet, Glucophage, Glucophage XR, Glumetza, Riomet

    HOW SUPPLIED

    Fortamet/Glucophage XR/Glumetza/Metformin Hydrochloride Oral Tab ER: 500mg, 750mg, 1000mg
    Glucophage/Metformin Hydrochloride Oral Tab: 500mg, 850mg, 1000mg
    Metformin Hydrochloride/Riomet Oral Sol: 5mL, 500mg

    DOSAGE & INDICATIONS

    For treatment of type 2 diabetes mellitus.
    For monotherapy or for use in combination with an insulin secretogue (e.g., sulfonylurea) or insulin.
    Oral dosage (regular-release tablets or oral solution)
    Adults

    Initially, 500 mg PO twice daily or 850 mg PO once daily, given with meals. In the geriatric adult, do not initiate therapy if 80 years old or older unless normal renal function is documented. Dosage increases should be made in increments of 500 mg weekly or 850 mg every 2 weeks, up to 2,000 mg/day PO, given in divided doses. Patients can also be titrated from 500 mg PO twice daily to 850 mg PO twice daily after 2 weeks. Doses above 2000 mg/day may be better tolerated if divided and given 3 times per day with meals. Max: 2,550 mg/day PO, in divided doses. In the geriatric adult, do not titrate to the maximum dosage. Many clinicians limit dose to 2 grams/day. Metformin is the initial drug therapy of choice for type 2 diabetes mellitus and should be initiated at the time of diagnosis in combination with lifestyle modifications in patients without any contraindications to therapy. If the maximum tolerated metformin dose does not achieve or maintain the HbA1c target over 3 months, add a second oral agent, a glucagon-like peptide 1 (GLP-1) receptor agonist, or insulin. When given with an insulin secretagogue (e.g., sulfonylurea) or insulin, lower doses of the insulin secretagogue or insulin may be needed to reduce the risk of hypoglycemia. For example, it is recommended that the insulin dose be decreased by 10% to 25% when fasting plasma glucose concentrations decrease to less than 120 mg/dL in patients receiving concomitant insulin and metformin. Further adjustment should be individualized based on glucose-lowering response.

    Children and Adolescents 10 years and older

    500 mg PO twice daily, given with meals. If needed, increase the daily dosage by 500 mg at weekly intervals. Max: 2,000 mg/day PO, given in divided doses. When given with an insulin secretagogue (e.g., sulfonylurea) or insulin, lower doses of the insulin secretagogue or insulin may be needed to reduce the risk of hypoglycemia. For example, it is recommended that the insulin dose be decreased by 10% to 25% when fasting plasma glucose concentrations decrease to less than 120 mg/dL in patients receiving concomitant insulin and metformin. Further adjustment should be individualized based on glucose-lowering response.

    Oral dosage (e.g., Glucophage XR extended-release tablets)
    Adults

    USUAL DOSE: 500 mg PO once daily with the evening meal. In the geriatric adult, do not initiate therapy if 80 years old or older unless normal renal function is documented. May increase daily dose by 500 mg/week as needed. Max: 2,000 mg PO once daily at the evening meal. If glycemic control is not achieved with 2,000 mg PO once daily, consider a trial of metformin XR 1,000 mg PO twice daily. If more than 2,000 mg/day is required, change to regular-release metformin in divided doses. IF SWITCHING FROM REGULAR-RELEASE METFORMIN: Give the same total daily dose of metformin, given PO once daily with the evening meal. Titrate in increments of 500 mg weekly as needed. Max: 2,000 mg/day PO. GUIDELINES: Metformin is the initial drug therapy of choice for type 2 diabetes mellitus and should be initiated at the time of diagnosis in combination with lifestyle modifications in patients without any contraindications to therapy. If the maximum tolerated metformin dose does not achieve or maintain the HbA1c target over 3 months, add a second oral agent, a glucagon-like peptide 1 (GLP-1) receptor agonist, or insulin. When given with an insulin secretagogue (e.g., sulfonylurea) or insulin, lower doses of the insulin secretagogue or insulin may be needed to reduce the risk of hypoglycemia. For example, it is recommended that the insulin dose be decreased by 10% to 25% when fasting plasma glucose concentrations decrease to less than 120 mg/dL in patients receiving concomitant insulin and metformin. Further adjustment should be individualized based on glucose-lowering response.

    Oral dosage (e.g., Fortamet extended-release film-coated tablets)
    Adults

    USUAL DOSE: 1,000 mg PO once daily with the evening meal, although 500 mg PO once daily with the evening meal may be used when clinically appropriate. May titrate in increments of no more than 500 mg/week. Max: 2,500 mg PO once daily with the evening meal. Generally, debilitated, geriatric, and malnourished patients should not be titrated to the maximum dose. IF SWITCHING FROM REGULAR-RELEASE METFORMIN: Give the same previous total daily dose of metformin once daily with the evening meal. Titrate in increments of 500 mg/week as needed. Max: 2,500 mg/day PO. GUIDELINES: Metformin is the initial drug therapy of choice for type 2 diabetes mellitus and should be initiated at the time of diagnosis in combination with lifestyle modifications in patients without any contraindications to therapy. If the maximum tolerated metformin dose does not achieve or maintain the HbA1c target over 3 months, add a second oral agent, a glucagon-like peptide 1 (GLP-1) receptor agonist, or insulin. When given with an insulin secretagogue (e.g., sulfonylurea) or insulin, lower doses of the insulin secretagogue or insulin may be needed to reduce the risk of hypoglycemia. For example, it is recommended that the insulin dose be decreased by 10% to 25% when fasting plasma glucose concentrations decrease to less than 120 mg/dL in patients receiving concomitant insulin and metformin. Further adjustment should be individualized based on glucose-lowering response.

    Oral dosage (Glumetza extended/modified-release tablets)
    Adults

    USUAL DOSE: 1,000 mg PO once daily with the evening meal. Increase in increments of 500 mg every 1 to 2 weeks as needed. Max: 2,000 mg PO once daily at the evening meal. If glycemic control is not achieved with 2,000 mg once daily, consider dividing the dose and giving a trial of 1,000 mg PO twice daily with meals. IF SWITCHING FROM REGULAR-RELEASE METFORMIN: Give the same total daily dose of metformin, given PO once daily with the evening meal. Titrate in increments of 500 mg weekly as needed. Max: 2,000 mg/day PO. GUIDELINES: Metformin is the initial drug therapy of choice for the management of type 2 diabetes mellitus and should be initiated at the time of diagnosis in combination with lifestyle modifications in patients without any contraindications to therapy. If the maximum tolerated metformin dose does not achieve or maintain the HbA1c target over 3 months, add a second oral agent, a glucagon-like peptide 1 (GLP-1) receptor agonist, or insulin. When given with an insulin secretagogue (e.g., sulfonylurea) or insulin, lower doses of the insulin secretagogue or insulin may be needed to reduce the risk of hypoglycemia. For example, it is recommended that the insulin dose be decreased by 10% to 25% when fasting plasma glucose concentrations decrease to less than 120 mg/dL in patients receiving concomitant insulin and metformin. Further adjustment should be individualized based on glucose-lowering response.

    For conversion to metformin monotherapy from other antidiabetic agents.
    Oral dosage
    Adults

    See dosage of metformin as per monotherapy. When transferring patients to metformin from standard oral hypoglycemic agents other than chlorpropamide, no transition period generally is necessary. When transferring patients from chlorpropamide, care should be exercised during the first 2 weeks because of the prolonged retention of chlorpropamide in the body, leading to overlapping drug effects and possible hypoglycemia.

    For the adjunct treatment of patients with hyperinsulinemia secondary to polycystic ovary syndrome† (PCOS), including the treatment of infertility† in these patients.
    Oral dosage (regular-release tablets)
    Adult females

    500 mg PO 3 times per day. After roughly 1 month, 33% of females with PCOS will ovulate compared to 4% with placebo. When metformin is added to clomiphene therapy for PCOS with infertility, roughly 86% of patients ovulate in comparison to roughly 8% on clomiphene alone. Worldwide data of metformin use in PCOS to regulate menstrual cycles and decrease ovarian steroidogenesis are relatively extensive. Metformin-failure may occur in severely obese patients, so weight loss and dietary control are also recommended.

    For the delay of clinical puberty and early menarche in females with precocious puberty†.
    Oral dosage
    Female children older than 6 years

    Limited data indicate that 425 mg PO once daily with dinner may be effective. Thirty-eight females with precocious puberty (average age at study initiation 7.9 +/- 0.2 years, average age at diagnosis of precocious puberty 6.8 +/- 0.2 years), low birth weight (less than 2.9 kg for term birth or -1SD for gestational age at preterm birth), and prepuberty (Tanner breast stage 1) were randomized to 425 mg of metformin at bedtime (n = 19) or no therapy (n = 19) in an open-label fashion; patients did not have a history of diabetes mellitus, adrenal hyperplasia, or thyroid abnormalities. After 24 months, patients treated with metformin experienced statistically significant improvements in metabolic abnormalities (i.e., insulin resistance, androgen excess, atherogenic lipid profile, and adipose body composition) as well as a 0.4 year delay in the clinical onset of puberty (defined as Tanner breast stage 2); additionally, metformin treatment was associated with a 1-year delay in the puberty-associated insulin-like growth factor-I rise. Preliminary 3-year data indicate that metformin treatment is associated with a delay in menarche (5/19 patients in the no treatment group have undergone menarche compared to 0/19 patients in the metformin-treated group, p = 0.016). Furthermore, the patients treated with metformin maintained gains in height and lean mass.

    For the prolongation of pubertal growth† and to prevent the delay of early menarche in low birth weight females with early-normal onset of puberty.
    Oral dosage
    Female children with onset of puberty between 8 and 9 years of age

    Limited data indicate that 825 mg PO once daily with dinner may be effective. Twenty-two females with onset of puberty (defined as Tanner breast stage 2) between 8 and 9 years of age (average age at onset 8.6 +/- 0.1 years) and low birth weight (2.8 kg or less for term birth or -1.5 SD for gestational age) were randomized to 850 mg metformin once daily (n = 10) or no treatment (n = 12) in an open-label fashion for 36 months. At enrollment, these patients had a height greater than or equal to 1 SD above midparenteral height for chronological age and bone age of greater than 1 year above chronological age; in addition, all patients had central and progressive puberty. Treatment with metformin resulted in a delay of menarche by a median of 1 year (p < 0.01) and increases in near-adult height (height gain over 42 months of treatment was 16 cm for the untreated group vs. 19.5 cm for the metformin-treated group, p <= 0.05). In addition, patients are still being followed and height has ceased in almost all of the patients in the untreated group, while 4/10 patients in the metformin-treated group continue to grow at a rate of greater than 2 cm/year. In addition, those patients receiving metformin had a leaner body composition and demonstrated lower levels of insulin resistance with improved lipid profiles.

    For the treatment of gestational diabetes† in patients not controlled by diet-therapy alone.
    Oral dosage (immediate-release dosage forms)
    Adults (pregnant females)

    500 mg PO once nightly for 1 week, then titrate to 500 mg PO twice daily. Further titration of the daily dose by 500 mg every 1 to 2 weeks to attain glycemic targets is used. Max: If needed, up to 2.5 to 3 grams/day PO, given in 2 or 3 divided doses, has been studied in gestational diabetes mellitus (GDM). Many studies and analyses of metformin in use in pregnancy have been published. However, metformin is not recommended for routine use during pregnancy. The American College of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association (ADA) continue to recommend human insulin as the standard of care in women with GDM requiring medical therapy. Per ACOG, in women who decline insulin therapy or are unable to safely administer insulin, metformin is the preferred second-line choice. Per the ADA, metformin may be used to treat GDM as a treatment option; however, metformin does cross the placenta. While no teratogenic effects have been associated with metformin, no long term safety data are available for any oral agent. Metformin may cause a lower risk of neonatal hypoglycemia and less maternal weight gain than insulin; however, some data suggest that metformin may slightly increase the risk of prematurity. The ADA notes that in some clinical studies, nearly 50% of GDM patients initially treated with metformin have needed the addition of insulin in order to achieve acceptable glucose control.

    †Indicates off-label use

    MAXIMUM DOSAGE

    Adults

    2550 mg/day PO for regular-release tablets and oral solution; 2000—2500 mg/day PO for extended-release tablets, depending on formulation used.

    Elderly

    In general, do not titrate to maximum doses (2550 mg/day PO for regular-release tablets and oral solution; 2000—2500 mg/day PO for extended-release tablets, depending on formulation used).

    Adolescents

    2000 mg/day PO for regular-release tablets and oral solution; safe and effective use has not been established for extended-release tablets.

    Children

    >= 10 years: 2000 mg/day PO for regular-release tablets and oral solution; safe and effective use has not been established for extended-release tablets.
    < 10 years: Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    Generally avoid metformin use in hepatic impairment; hepatic disease increases the risk of metformin-associated lactic acidosis.

    Renal Impairment

    eGFR more than 45 mL/minute/1.73 m2: No dosage adjustment needed. Obtain an eGFR at least annually in all patients taking metformin.
    eGFR 30 to 45 mL/minute/1.73 m2: Initiation of metformin is not recommended. Obtain an eGFR at least annually in all patients taking metformin. In patients whose eGFR is initially greater than 45 mL/minute/1.73 m2, and then later falls below 45 mL/minute/1.73 m2, assess the benefits and risks of continuing treatment. Discontinue metformin if the patient's eGFR later falls below 30 mL/minute/1.73 m2. The ADA and others suggest it is reasonable to decrease the dose by 50% (or use one-half the maximum recommended dose) and monitor renal function every 3 months in those with an eGFR less than 45 mL/minute/1.73 m2. Do not initiate the drug in patients at this stage. Additional caution is required in patients with anticipated significant fluctuations in renal status or those at risk for abrupt deterioration in kidney function, based on previous history, other comorbidities, albuminuria, and medication regimen (e.g., potent diuretics or nephrotoxic agents).
    eGFR less than 30 mL/minute/1.73 m2: Use is contraindicated.
     
    Intermittent hemodialysis
    Metformin use is contraindicated. Metformin is dialyzable; hemodialysis will efficiently remove accumulated metformin in the case of drug-induced lactic acidosis, provided metformin is halted.

    ADMINISTRATION

    Oral Administration
    Oral Solid Formulations

    Regular-release tablets: Administer orally with meals.
    Extended-release tablets: Do not crush or chew; swallow whole. Usually administered once-daily with the evening meal. The inactive ingredients may occasionally be eliminated in the feces as a soft mass that may resemble the original tablet.

    Oral Liquid Formulations

    Oral Solution: Use a calibrated spoon, oral syringe, or container to measure the oral solution for accurate dosing. Administer orally with meals.

    STORAGE

    Fortamet:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F
    Glucophage:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F
    Glucophage XR:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F
    Glumetza:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F
    Riomet:
    - Store at room temperature (between 59 to 86 degrees F)

    CONTRAINDICATIONS / PRECAUTIONS

    General Information

    Do not use metformin in patients who have a known metformin hypersensitivity.

    Diabetic ketoacidosis, type 1 diabetes mellitus

    Metformin should not be used for Type 1 diabetes mellitus. Metformin is not an effective treatment of and use is contraindicated in diabetic ketoacidosis (DKA). DKA, with or without coma; DKA should be treated with insulin.

    Acidemia, hypoxemia, lactic acidosis, metabolic acidosis

    Metformin is contraindicated in patients with metabolic acidosis. Metformin is associated with a risk for lactic acidosis and therefore should not be used in patients with lactic acidosis, a form of metabolic acidosis. Lactic acidosis should be suspected in any diabetic patient with metabolic acidosis lacking evidence of ketoacidosis (ketonuria and ketonemia). Lactic acidosis is a rare but serious complication that can occur due to metformin accumulation; when it occurs, it is fatal in approximately 50% of cases. Lactic acidosis may also occur in association with a number of pathophysiologic conditions, including diabetes mellitus, and whenever there is significant tissue hypoperfusion and hypoxemia or significant renal dysfunction. Certain medications used concomitantly with metformin may also increase the risk of lactic acidosis. Lactic acidosis is characterized by elevated blood lactate levels, acidemia, electrolyte disturbances, an increased anion gap, and an increased lactate/pyruvate ratio. When metformin is implicated as the cause of lactic acidosis, metformin plasma levels more than 5 mcg/mL are generally found. The reported incidence of lactic acidosis in patients receiving metformin is very low; in more than 20,000 patient-years exposure to metformin in clinical trials, there have been no reports of lactic acidosis and approximately 0.03 cases/1,000 patient-years have been estimated with post-marketing surveillance. A nested case-control study of 50,048 patients with type 2 diabetes mellitus demonstrated that during concurrent use of oral diabetes drugs, there were 6 identified cases of lactic acidosis. The crude incidence rate was 3.3 cases per 100,000 person-years in patients treated with metformin; it should be noted that all of the subjects had relevant comorbidities known to be risk factors for lactic acidosis. The onset of lactic acidosis often is subtle, and accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, increasing somnolence, and nonspecific abdominal distress. There may be associated hypothermia, hypotension, and resistant bradycardia with more marked acidemia. The patient and the prescriber must be aware of such symptoms and the patient should be instructed to notify the physician immediately if they occur. Metformin should be withdrawn until the situation is clarified. Serum electrolytes, ketones, blood glucose, and if indicated, blood pH, lactate levels, and even blood metformin levels may be useful.

    Diarrhea, vomiting

    Gastrointestinal (GI) side effects are common during metformin initiation. However, once a patient is stabilized on any dose of metformin, GI symptoms are unlikely to be drug related. Later occurrence of GI symptoms may be due to a change in clinical status and may increase the risk of lactic acidosis or other serious disease. Patients stable on metformin therapy who complain of an increase in GI symptoms should undergo laboratory investigation to determine the etiology of the GI symptoms. These include, but are not limited to, diarrhea and nausea/vomiting. Furthermore, withholding metformin therapy until the cause of the GI symptoms is known may be necessary. Finally, diarrhea and nausea/vomiting may alter gastric emptying and caloric intake, which could all affect blood glucose control, especially increasing the risk of low blood glucose. Patients should be advised to contact their prescriber if an increase in gastrointestinal symptoms occurs while taking metformin; patients should also be advised to monitor their blood glucose concentrations more frequently.

    Renal disease, renal failure, renal impairment

    Metformin is substantially eliminated by the kidney and the risk of lactic acidosis increases with the degree of intrinsic renal disease or impairment. Certain medications that are eliminated via the kidney when used concomitantly with metformin may also increase the risk of lactic acidosis. Prior to initiating treatment in any patient, obtain an estimated glomerular filtration rate (eGFR) to assess renal function. Metformin is contraindicated for use in patients with renal failure or severe renal impairment (defined as eGFR below 30 mL/minute/1.73 m2). Initiating metformin in patients with an eGFR between 30 to 45 mL/minute/1.73 m2 is not recommended. Obtain an eGFR at least annually in all patients taking metformin. In those patients at increased risk for the development of renal impairment such as the elderly, renal function should be assessed more frequently. In patients taking metformin whose eGFR later falls below 45 mL/minute/1.73 m2, assess the benefits and risks of continuing treatment. Discontinue metformin if the patient’s eGFR later falls below 30 mL/minute/1.73 m2. Based on the results of a comprehensive FDA safety review, the FDA concluded that metformin can be used safely in patients with mild renal impairment, and in some patients with moderate renal impairment. The measure of kidney function used to determine whether a patient can receive metformin has been changed from serum creatinine to the eGFR; this is because in addition to serum creatinine concentration, the eGFR takes into account additional parameters that are important, such as the patient’s age, gender, race and/or weight.

    Acute heart failure, acute myocardial infarction, cardiac disease, cardiogenic shock, heart failure

    According to the manufacturer, metformin should be used with caution in patients with congestive heart failure requiring pharmacologic treatment. However, a systematic review evaluating antidiabetic agents and outcomes in patients with heart failure and diabetes concluded that metformin is not associated with any measurable harm in patients with heart failure; in this analysis, metformin was associated with reduced mortality. It should be noted that in acute congestive heart failure characterized by acute hypoxia, lactic acidosis has occurred in patients taking metformin. To reduce the risk of lactic acidosis, metformin should be promptly withheld in the presence of any condition associated with hypoxemia. Acute hypoxia and acute cardiac disease (e.g., acute heart failure, cardiogenic shock, or acute myocardial infarction) and other conditions characterized by acute hypoxia have been associated with the development of lactic acidosis and may cause prerenal azotemia. If such events occur, discontinue metformin.

    Alcoholism, ethanol ingestion, ethanol intoxication, hepatic disease

    Metformin administration increases the risk for lactic acidosis. Since the liver is important for clearing accumulated lactic acid, metformin is not recommended in patients with clinical or laboratory evidence of hepatic disease as the risk of lactic acidosis may be increased. Hepatic disease also causes altered gluconeogenesis, which may affect glycemic control. Alcohol is known to potentiate the effect of metformin on lactate metabolism. Patients should be warned against excessive ethanol ingestion (ethanol intoxication) while taking metformin due to the increased risk for lactic acidosis. Those with ethanol intoxication are also particularly susceptible to hypoglycemic effects of oral antidiabetic agents. Metformin use should be avoided by those patients with alcoholism.

    Radiographic contrast administration

    Discontinue metformin at the time of or before radiographic contrast administration in patients with an estimated glomerular filtration rate (eGFR) between 30 and 60 mL/minute/1.73 m2; in patients with a history of hepatic disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinated contrast. Re-evaluate eGFR the 48 hours after the imaging procedure; restart metformin if renal function is stable.

    Burns, dehydration, fever, infection, sepsis, surgery, trauma

    To reduce the risk of lactic acidosis, metformin should be promptly withheld in the presence of any condition associated with hypoxemia, dehydration, or sepsis. Metformin therapy should be temporarily suspended for any surgery, except for minor procedures where intake of fluids and food is not restricted. Do not restart this drug until oral intake is resumed and renal function has been evaluated as normal. Temporary use of insulin in place of oral antidiabetic agents may be necessary during periods of physiologic stress (e.g., burns, systemic infection, trauma, surgery, or fever). Any change in clinical status, including diarrhea or vomiting, may also increase the risk of lactic acidosis and may require laboratory evaluation in patients on metformin and may require the drug be withheld.

    Adrenal insufficiency, gastroparesis, GI obstruction, hypercortisolism, hyperglycemia, hyperthyroidism, hypoglycemia, hypothyroidism, ileus, malnutrition, pituitary insufficiency

    Delayed stomach emptying may alter blood glucose control; monitor patients with diarrhea, gastroparesis, GI obstruction, ileus, or vomiting carefully. Conditions that predispose patients to developing hypoglycemia or hyperglycemia may alter antidiabetic agent efficacy. Hyperglycemia related conditions include drug interactions, female hormonal changes, high fever, severe psychological stress, and uncontrolled hypercortisolism or hyperthyroidism. Metformin causes hypoglycemia infrequently in the absence of risk factors as monotherapy. Conditions associated with an increased risk for hypoglycemia include debilitated physical condition, drug interactions, malnutrition, uncontrolled adrenal insufficiency, pituitary insufficiency or hypothyroidism. More frequent blood glucose monitoring may be necessary in patients with these conditions while receiving metformin. There is also an increased risk of hypoglycemia when metformin is combined with insulin or an insulin secretagogue (e.g., sulfonylureas). Therefore, a lower dose of insulin or an insulin secretagogue may be required to minimize the risk of hypoglycemia when used in combination with metformin. Monitor blood glucose.

    Pernicious anemia

    Metformin may result in suboptimal vitamin B12 absorption, possibly due to interference with the B12-intrinsic factor complex. The interaction very rarely results in a pernicious anemia that appears reversible with discontinuation of metformin or with cyanocobalamin supplementation. Certain individuals may be predisposed to this type of anemia; a nested case-control study of 465 patients taking metformin (155 with vitamin B12 deficiency and 310 without) demonstrated that dose and duration of metformin use may be associated with an increased odds of vitamin B12 deficiency. Each 1 gram/day increment in dose significantly increased the odds of vitamin B12 deficiency (OR 2.88, 95% CI 2.15 to3.87) as did taking metformin for 3 years or more (OR 2.39, 95% CI 1.46 to 3.91). Regular measurement of hematologic parameters is recommended in all patients on chronic metformin treatment.

    Geriatric

    Controlled clinical studies of metformin did not include sufficient numbers of older patients to determine whether they respond differently from younger patients, although other reported clinical experience has not identified differences in responses between geriatric and younger adult patients. Use metformin with caution in geriatric patients. Metformin is substantially excreted by the kidney and the risk of adverse reactions (including lactic acidosis) is greater in patients with reduced renal function. Because aging is associated with renal function decline, care should be taken with dose selection and titration. Obtain an estimated glomerular filtration rate (eGFR) at least annually in all patients taking metformin. In patients at increased risk for the development of renal impairment such as geriatric patients, renal function should be assessed more frequently. Unless estimated renal function via the eGFR is determined to be normal, do not use metformin in geriatric patients 80 years of age and older. Generally, elderly or debilitated patients should not be titrated up to maximum metformin dosages. Elderly, debilitated, or malnourished patients are also particularly susceptible to hypoglycemic effects of antidiabetic agents; monitor blood glucose frequently. The federal Omnibus Budget Reconciliation Act (OBRA) regulates medication use in residents of long-term care facilities (LTCFs). According to OBRA, the use of antidiabetic medications should include monitoring (e.g., periodic blood glucose) for effectiveness based on desired goals for that individual and to identify complications of treatment such as hypoglycemia or impaired renal function. Metformin has been associated with lactic acidosis, which is more likely to occur under the following conditions: serum creatinine of 1.5 mg/dL or higher in males or 1.4 mg/dL or higher in females, abnormal creatinine clearance from any cause, age of 80 years or older unless measurement of creatinine clearance verifies normal renal function, radiologic studies in which intravascular iodinated contrast materials are given, congestive heart failure requiring pharmacologic management, or acute/chronic metabolic acidosis with or without coma (including diabetic ketoacidosis).

    Polycystic ovary syndrome, pregnancy

    Premenopausal anovulatory females with insulin resistance (i.e., those with polycystic ovary syndrome (PCOS)) may resume ovulation as a result of metformin therapy; patients may be at risk of conception if adequate contraception is not used in those not desiring to become pregnant. In some cases, metformin is used as an adjunct in PCOS patients to regulate menstrual cycles or to enhance fertility. Metformin is not recommended for routine use during pregnancy. Metformin does pass through the placenta and the fetus is likely exposed to therapeutic concentrations of metformin. The American College of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association (ADA) continue to recommend human insulin as the standard of care in women with gestational diabetes mellitus (GDM) requiring medical therapy. Per ACOG, in women who decline insulin therapy or are unable to safely administer insulin, metformin is the preferred second-line choice. Per the ADA, metformin may be used to treat GDM as a treatment option; however, no long term safety data are available for any oral agent. Metformin may cause a lower risk of neonatal hypoglycemia and less maternal weight gain than insulin; however, some data suggest that metformin may slightly increase the risk of prematurity. The ADA notes that in some clinical studies, nearly 50% of GDM patients initially treated with metformin have needed the addition of insulin in order to achieve acceptable glucose control. Many studies and analyses of metformin in use in pregnancy have been published. Data suggest no increase in the rates of expected birth defects or other adverse outcomes in exposed infants and studies comparing metformin to insulin in the treatment of gestational diabetes have generally found no significant differences in glycemic control or pregnancy outcomes.

    Breast-feeding

    Small studies indicate that metformin is excreted in human breast milk. Infant hypoglycemia or other side effects are a possibility; however, adverse effects on infant plasma glucose have not been reported in human studies. Animal data show that metformin is excreted into breast milk and reaches levels similar to those in plasma. Furthermore, the use of metformin 2550 mg/day by mothers breast-feeding their infants for 6 months does not affect growth, motor, or social development; the effects beyond 6 months are not known. In all of these studies, the estimated weight-adjusted infant exposure to metformin ranged from 0.11% to 1.08% of the mother's dose. While the manufacturers of metformin recommend that a decision should be made to discontinue breast-feeding or discontinue the drug, the results of these studies indicate that maternal ingestion of metformin during breast-feeding is probably safe to the infant. However, a risk and benefit analysis should be made for each mother and her infant; if patients elect to continue metformin while breast-feeding, the mother should be aware of the potential risks to the infant. If metformin is discontinued and blood glucose is not controlled on diet and exercise alone, insulin therapy should be considered. Because acarbose has limited systemic absorption, which results in minimal maternal plasma concentrations, clinically significant exposure via breast milk is not expected ; therefore, this agent may represent a reasonable alternative for some patients. Tolbutamide is usually considered compatible with breast-feeding. Glyburide may be a suitable alternative since it was not detected in the breast milk of lactating women who received single and multiple doses of glyburide. If any oral hypoglycemics are used during breast feeding, the nursing infant should be monitored for signs of hypoglycemia, such as increased fussiness or somnolence.

    Children

    The safety and effectiveness of metformin have not been established in children under the age 10 years; in general, there are limited experiences with metformin use in pediatric patients with type 2 diabetes mellitus. Experiences with metformin in children and adolescents 10 to 16 years of age has demonstrated similar glycemic control to adults. The extended-release dosage forms of metformin have not been FDA approved for use in pediatric patients.

    ADVERSE REACTIONS

    Severe

    megaloblastic anemia / Delayed / 0-1.0
    lactic acidosis / Delayed / 0-0.1
    rhabdomyolysis / Delayed / Incidence not known

    Moderate

    vitamin B12 deficiency / Delayed / 7.0-7.0
    hypoglycemia / Early / 1.0-5.0
    palpitations / Early / 1.0-5.0
    chest pain (unspecified) / Early / 1.0-5.0
    metabolic acidosis / Delayed / 0-0.1
    folate deficiency / Delayed / Incidence not known
    cholestasis / Delayed / Incidence not known
    hepatitis / Delayed / Incidence not known
    elevated hepatic enzymes / Delayed / Incidence not known

    Mild

    diarrhea / Early / 9.6-53.2
    vomiting / Early / 6.5-25.5
    nausea / Early / 6.5-25.5
    flatulence / Early / 1.0-12.1
    dyspepsia / Early / 1.0-7.1
    abdominal pain / Early / 1.0-6.4
    headache / Early / 5.7-5.7
    dysgeusia / Early / 1.0-5.0
    metallic taste / Early / 1.0-5.0
    anorexia / Delayed / 1.0-5.0
    myalgia / Early / 1.0-5.0
    malaise / Early / 1.0-5.0
    rash / Early / 1.0-5.0
    hyperhidrosis / Delayed / 1.0-5.0
    chills / Rapid / 1.0-5.0
    infection / Delayed / 1.0-5.0
    flushing / Rapid / 1.0-5.0
    dizziness / Early / 1.0-5.0
    weight loss / Delayed / 10.0

    DRUG INTERACTIONS

    Abacavir; Dolutegravir; Lamivudine: (Major) Caution is advised when administering dolutegravir with metformin, as coadministration may increase exposure to metformin. Increased exposure to metformin may increase the risk for hypoglycemia, gastrointestinal side effects, and potentially increase the risk for lactic acidosis. If these drugs are used in combination, the total daily dose of metformin must not exceed 1000 mg/day. Close monitoring of blood glucose and patient clinical status is recommended. When stopping dolutegravir, the metformin dose may need to be adjusted. In drug interaction studies, dolutegravir increased both the Cmax and AUC of metformin when metformin was administered at a dose of 500 mg PO twice daily. Dolutegravir inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k]). (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems.
    Abacavir; Lamivudine, 3TC: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems.
    Abacavir; Lamivudine, 3TC; Zidovudine, ZDV: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Chlorpheniramine; Phenylephrine; Phenyltoloxamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Dextromethorphan; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Dextromethorphan; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Guaifenesin; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetaminophen; Propoxyphene: (Moderate) Propoxyphene may enhance the hypoglycemic action of antidiabetic agents. Patients should be closely monitored for changes in glycemic control while receiving propoxyphene in combination with antidiabetic agents.
    Acetaminophen; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Acetazolamide: (Moderate) Carbonic anhydrase inhibitors may alter blood sugar. Both hyperglycemia and hypoglycemia have been described in patients treated with acetazolamide. This should be taken into consideration in patients with impaired glucose tolerance or diabetes mellitus who are receiving antidiabetic agents. Monitor blood glucose and for changes in glycemic control and be alert for evidence of an interaction. Carbonic anhydrase inhibitors frequently decrease serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. Use these drugs with caution in patients treated with metformin, as the risk of lactic acidosis may increase. Monitor electrolytes and renal function.
    Acetohexamide: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Acrivastine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Adefovir: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., adefovir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Aliskiren; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Aliskiren; Hydrochlorothiazide, HCTZ: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Aliskiren; Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Amiloride; Hydrochlorothiazide, HCTZ: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Amlodipine; Benazepril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Amlodipine; Hydrochlorothiazide, HCTZ; Olmesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Amlodipine; Hydrochlorothiazide, HCTZ; Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Amlodipine; Olmesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Amlodipine; Telmisartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Amlodipine; Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Amoxicillin; Clarithromycin; Lansoprazole: (Moderate) The concomitant use of clarithromycin and antidiabetic agents can result in significant hypoglycemia. Careful monitoring of blood glucose is recommended.
    Amoxicillin; Clarithromycin; Omeprazole: (Moderate) The concomitant use of clarithromycin and antidiabetic agents can result in significant hypoglycemia. Careful monitoring of blood glucose is recommended.
    Amphetamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Amphetamine; Dextroamphetamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Amphetamines: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Androgens: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Angiotensin II receptor antagonists: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Angiotensin-converting enzyme inhibitors: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Atazanavir; Cobicistat: (Moderate) Concurrent administration of metformin and cobicistat may increase the risk of lactic acidosis. Cobicistat is a potent inhibitor of the human multidrug and toxic extrusion 1 (MATE1) on proximal renal tubular cells; metformin is a MATE1 substrate. Inhibition of MATE1 by cobicistat may decrease metformin eliminiation by blocking renal tubular secretion. If these drugs are given together, closely monitor for signs of metformin toxicity; metformin dose adjustments may be needed.
    Atenolol; Chlorthalidone: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    atypical antipsychotic: (Moderate) Atypical antipsychotic therapy may aggravate diabetes mellitus and cause metabolic changes such as hyperglycemia. Monitor patients on antidiabetic agents for worsening glycemic control. The atypical antipsychotics have been associated with metabolic changes, including hyperglycemia, diabetic ketoacidosis, hyperosmolar, hyperglycemic states, and diabetic coma. Aggravation of diabetes mellitus has been reported. Possible mechanisms include atypical antipsychotic-induced insulin resistance or direct beta-cell inhibition.
    Azelaic Acid; Copper; Folic Acid; Nicotinamide; Pyridoxine; Zinc: (Moderate) Niacin (nicotinic acid) interferes with glucose metabolism and can result in hyperglycemia. Changes in glycemic control can usually be corrected through modification of hypoglycemic therapy. Monitor patients taking antidiabetic agents for changes in glycemic control if niacin (nicotinic acid) is added or deleted to the medication regimen. Dosage adjustments may be necessary. (Moderate) Niacin interferes with glucose metabolism and can result in hyperglycemia. When used at daily doses of 750 to 2000 mg, niacin significantly lowers LDL cholesterol and triglycerides while increasing HDL cholesterol. Changes in glycemic control can usually be corrected through modification of hypoglycemic therapy. Monitor patients on antidiabetic therapy for blood glucose control if niacin (nicotinic acid) is added or deleted to the medication regimen. Dosage adjustments may be necessary. (Minor) Levomefolate and metformin should be used together cautiously. Plasma concentrations of levomefolate may be reduced during treatment of type 2 diabetes with metformin. Monitor patients for decreased efficacy of levomefolate if these agents are used together.
    Azilsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Azilsartan; Chlorthalidone: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Benazepril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Benazepril; Hydrochlorothiazide, HCTZ: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Bendroflumethiazide; Nadolol: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Benzphetamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Beta-blockers: (Moderate) Increased frequency of blood glucose monitoring may be required when a beta blocker is given with antidiabetic agents. Since beta blockers inhibit the release of catecholamines, these medications may hide symptoms of hypoglycemia such as tremor, tachycardia, and blood pressure changes. Other symptoms, like headache, dizziness, nervousness, mood changes, or hunger are not blunted. Beta-blockers also exert complex actions on the body's ability to regulate blood glucose. Some beta-blockers, particularly non-selective beta-blockers such as propranolol, have been noted to potentiate insulin-induced hypoglycemia and a delay in recovery of blood glucose to normal levels. Hyperglycemia has been reported as well and is possibly due to beta-2 receptor blockade in the beta cells of the pancreas. A selective beta-blocker may be preferred in patients with diabetes mellitus, if appropriate for the patient's condition. Selective beta-blockers, such as atenolol or metoprolol, do not appear to potentiate insulin-induced hypoglycemia. While beta-blockers may have negative effects on glycemic control, they reduce the risk of cardiovascular disease and stroke in patients with diabetes and their use should not be avoided in patients with compelling indications for beta-blocker therapy when no other contraindications are present.
    Bictegravir; Emtricitabine; Tenofovir Alafenamide: (Moderate) Caution is advised when administering bictegravir with metformin, as coadministration may increase exposure to metformin and increase the risk for hypoglycemia, gastrointestinal side effects, and potentially increase the risk for lactic acidosis. Close monitoring of blood glucose and patient clinical status is recommended. In drug interaction studies, bictegravir increased both the Cmax and AUC of metformin at a metformin dose of 500 mg PO twice daily. Bictegravir inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1]). (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Bisoprolol; Hydrochlorothiazide, HCTZ: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Bortezomib: (Moderate) During clinical trials of bortezomib, hypoglycemia and hyperglycemia were reported in diabetic patients receiving antidiabetic agents. Patients taking antidiabetic agents and receiving bortezomib treatment may require close monitoring of their blood glucose levels and dosage adjustment of their medication.
    Brompheniramine; Carbetapentane; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Brompheniramine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Bumetanide: (Minor) Bumetanide has been associated with hyperglycemia, possibly due to potassium depletion, and, glycosuria has been reported. Because of this, a potential pharmacodynamic interaction exists between bumetanide and all antidiabetic agents. This interference can lead to a loss of diabetic control, so diabetic patients should be monitored closely.
    Candesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Candesartan; Hydrochlorothiazide, HCTZ: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Captopril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Captopril; Hydrochlorothiazide, HCTZ: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Carbetapentane; Chlorpheniramine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbetapentane; Diphenhydramine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbetapentane; Guaifenesin; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbetapentane; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbetapentane; Phenylephrine; Pyrilamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbetapentane; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbinoxamine; Dextromethorphan; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbinoxamine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Carbinoxamine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Cephalexin: (Moderate) In healthy subjects given single 500 mg doses of cephalexin and metformin, plasma metformin Cmax and AUC increased by an average of 34% and 24%, respectively; metformin renal clearance decreased by an average of 14%. No information is available about the interaction of cephalexin and metformin following multiple dose administration.
    Cetirizine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlophedianol; Dexchlorpheniramine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlophedianol; Guaifenesin; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chloroquine: (Major) Careful monitoring of blood glucose is recommended when chloroquine and antidiabetic agents, including metformin, are coadministered. A decreased dose of the antidiabetic agent may be necessary as severe hypoglycemia has been reported in patients treated concomitantly with chloroquine and an antidiabetic agent.
    Chlorothiazide: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Hydrocodone; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Hydrocodone; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpheniramine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Chlorpropamide: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Chlorthalidone: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Chlorthalidone; Clonidine: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary. (Minor) Increased frequency of blood glucose monitoring may be required when clonidine is given with antidiabetic agents. Since clonidine inhibits the release of catecholamines, clonidine may hide symptoms of hypoglycemia such as tremor, tachycardia, and blood pressure changes. Other symptoms, like headache, dizziness, nervousness, mood changes, or hunger are not blunted. Clonidine does not appear to impair recovery from hypoglycemia, and has not been found to impair glucose tolerance in diabetic patients.
    Chromium: (Moderate) Chromium dietary supplements may lower blood glucose. As part of the glucose tolerance factor molecule, chromium appears to facilitate the binding of insulin to insulin receptors in tissues and to aid in glucose metabolism. Because blood glucose may be lowered by the use of chromium, patients who are on antidiabetic agents may need dose adjustments. Close monitoring of blood glucose is recommended.
    Cimetidine: (Moderate) Caution is advised when administering cimetidine with metformin. Cimetidine inhibits renal elimination of metformin. Increased metformin exposure may lead to hypoglycemia, gastrointestinal complaints, and an increased risk for lactic acidosis. Consider alternatives to cimetidine. If medically necessary to use cimetidine, carefully monitor. Metformin dose reduction may be needed. An interaction between metformin and oral cimetidine has been observed in normal healthy volunteers in both single- and multiple-dose, metformin-cimetidine drug interaction studies, with a 60% increase in peak metformin plasma and whole blood concentrations and a 40% increase in plasma and whole blood metformin AUC. There was no change in elimination half-life in the single-dose study. Cimetidine inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k]).
    Ciprofloxacin: (Moderate) Careful monitoring of blood glucose is recommended when quinolones and antidiabetic agents, including metformin, are coadministered. Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones and an antidiabetic agent.
    Cisapride: (Moderate) Because cisapride can enhance gastric emptying in diabetic patients, blood glucose can be affected, which, in turn, may affect the clinical response to antidiabetic agents. Monitor blood glucose and adjust if cliniically indicated.
    Clarithromycin: (Moderate) The concomitant use of clarithromycin and antidiabetic agents can result in significant hypoglycemia. Careful monitoring of blood glucose is recommended.
    Clofarabine: (Moderate) Concomitant use of clofarabine and metformin may result in altered clofarabine levels because both agents are a substrate of OCT1. Therefore, monitor for signs of clofarabine toxicity such as gastrointestinal toxicity (e.g., nausea, vomiting, diarrhea, mucosal inflammation), hematologic toxicity, and skin toxicity (e.g. hand and foot syndrome, rash, pruritus) in patients also receiving OCT1 substrates.
    Clonidine: (Minor) Increased frequency of blood glucose monitoring may be required when clonidine is given with antidiabetic agents. Since clonidine inhibits the release of catecholamines, clonidine may hide symptoms of hypoglycemia such as tremor, tachycardia, and blood pressure changes. Other symptoms, like headache, dizziness, nervousness, mood changes, or hunger are not blunted. Clonidine does not appear to impair recovery from hypoglycemia, and has not been found to impair glucose tolerance in diabetic patients.
    Cobicistat: (Moderate) Concurrent administration of metformin and cobicistat may increase the risk of lactic acidosis. Cobicistat is a potent inhibitor of the human multidrug and toxic extrusion 1 (MATE1) on proximal renal tubular cells; metformin is a MATE1 substrate. Inhibition of MATE1 by cobicistat may decrease metformin eliminiation by blocking renal tubular secretion. If these drugs are given together, closely monitor for signs of metformin toxicity; metformin dose adjustments may be needed.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Alafenamide: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Concurrent administration of metformin and cobicistat may increase the risk of lactic acidosis. Cobicistat is a potent inhibitor of the human multidrug and toxic extrusion 1 (MATE1) on proximal renal tubular cells; metformin is a MATE1 substrate. Inhibition of MATE1 by cobicistat may decrease metformin eliminiation by blocking renal tubular secretion. If these drugs are given together, closely monitor for signs of metformin toxicity; metformin dose adjustments may be needed.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Disoproxil Fumarate: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Concurrent administration of metformin and cobicistat may increase the risk of lactic acidosis. Cobicistat is a potent inhibitor of the human multidrug and toxic extrusion 1 (MATE1) on proximal renal tubular cells; metformin is a MATE1 substrate. Inhibition of MATE1 by cobicistat may decrease metformin eliminiation by blocking renal tubular secretion. If these drugs are given together, closely monitor for signs of metformin toxicity; metformin dose adjustments may be needed.
    Codeine; Phenylephrine; Promethazine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes. (Minor) Promethazine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Phenothiazines have been reported to increase blood glucose concentrations.
    Codeine; Promethazine: (Minor) Promethazine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Phenothiazines have been reported to increase blood glucose concentrations.
    Colesevelam: (Moderate) Colesevelam increases the Cmax and AUC of extended-release metformin (metformin ER) by approximately 8% and 44%, respectively. According to the manufacturer of colesevelam, the clinical response to metformin ER should be monitored in patients receiving concomitant therapy. Colesevelam has no significant effect on the bioavailability of immediate-release metformin.
    Conjugated Estrogens: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Conjugated Estrogens; Bazedoxifene: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Conjugated Estrogens; Medroxyprogesterone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Corticosteroids: (Moderate) Monitor patients receiving antidiabetic agents closely for worsening glycemic control when corticosteroids are instituted and for signs of hypoglycemia when corticosteroids are discontinued. Systemic and inhaled corticosteroids are known to increase blood glucose and worsen glycemic control in patients taking antidiabetic agents. The main risk factors for impaired glucose tolerance due to corticosteroids are the dose of steroid and duration of treatment. Corticosteroids stimulate hepatic glucose production and inhibit peripheral glucose uptake into muscle and fatty tissues, producing insulin resistance. Decreased insulin production may occur in the pancreas due to a direct effect on pancreatic beta cells.
    Crizotinib: (Moderate) Monitor for an increase in metformin-related adverse reactions and toxicities (e.g., lactic acidosis) if coadministration with crizotinib is necessary; consider the risks and benefits of coadministration. Metformin is a substrate of the renal uptake transporter, OCT2. Crizotinib inhibits OCT2 at clinically relevant concentrations, and has the potential to increase plasma concentrations of drugs that are substrates of OCT2. Coadministration with another OCT2 inhibitor increased the Cmax and AUC of metformin by 60% and 40%, respectively; there was no change in the elimination half-life of metformin.
    Cyanocobalamin, Vitamin B12: (Minor) Metformin may result in suboptimal oral vitamin B12 absorption by competitively blocking the calcium-dependent binding of the intrinsic factor-vitamin B12 complex to its receptor. Regular measurement of hematologic parameters is recommended in all patients on chronic metformin treatment; abnormalities should be investigated.
    Cyclosporine: (Moderate) Patients should be monitored for worsening glycemic control if therapy with cyclosporine is initiated in patients receiving antidiabetic agents. Cyclosporine has been reported to cause hyperglycemia or exacerbate diabetes mellitus; this effect appears to be dose-related and caused by direct beta-cell toxicity. Also, any drug that deteriorates the renal status of the patient is likely to alter metformin concentrations in the body, so renal function should be carefully monitored during the use of cyclosporine and metformin together.
    Danazol: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Darunavir; Cobicistat: (Moderate) Concurrent administration of metformin and cobicistat may increase the risk of lactic acidosis. Cobicistat is a potent inhibitor of the human multidrug and toxic extrusion 1 (MATE1) on proximal renal tubular cells; metformin is a MATE1 substrate. Inhibition of MATE1 by cobicistat may decrease metformin eliminiation by blocking renal tubular secretion. If these drugs are given together, closely monitor for signs of metformin toxicity; metformin dose adjustments may be needed.
    Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Concurrent administration of metformin and cobicistat may increase the risk of lactic acidosis. Cobicistat is a potent inhibitor of the human multidrug and toxic extrusion 1 (MATE1) on proximal renal tubular cells; metformin is a MATE1 substrate. Inhibition of MATE1 by cobicistat may decrease metformin eliminiation by blocking renal tubular secretion. If these drugs are given together, closely monitor for signs of metformin toxicity; metformin dose adjustments may be needed.
    Dasabuvir; Ombitasvir; Paritaprevir; Ritonavir: (Major) While no dosage adjustment of metformin is recommended in patients with normal hepatic or renal function, careful patient monitoring and dose adjustment of metformin and/or the potentially interfering drug is recommended with concurrent use. Monitor for signs of onset of lactic acidosis such as respiratory distress, somnolence, and non-specific abdominal distress or worsening renal function. Do not use metformin with paritaprevir in patients with renal insufficiency or hepatic impairment. Drugs that interfere with common renal tubular transport systems involved in the renal elimination of metformin could increase systemic exposure to metformin and may increase the risk for lactic acidosis. Paritaprevir is an inhibitor of the organic anion transporters OATP1B1 and OATP1B3. While initial drug-drug interaction studies of paritaprevir-containing hepatitis treatments have not noted an effect on metformin concentrations, more study is needed.
    Desloratadine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Dexchlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Dextroamphetamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Dextromethorphan; Diphenhydramine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Dextromethorphan; Guaifenesin; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Dextromethorphan; Guaifenesin; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Dextromethorphan; Promethazine: (Minor) Promethazine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Phenothiazines have been reported to increase blood glucose concentrations.
    Diazoxide: (Minor) Diazoxide, when administered intravenously or orally, produces a prompt dose-related increase in blood glucose level, due primarily to an inhibition of insulin release from the pancreas, and also to an extrapancreatic effect. The hyperglycemic effect begins within an hour and generally lasts no more than 8 hours in the presence of normal renal function. The hyperglycemic effect of diazoxide is expected to be antagonized by certain antidiabetic agents (e.g., insulin or a sulfonylurea). Blood glucose should be closely monitored.
    Dichlorphenamide: (Moderate) Use dichlorphenamide and metformin together with caution. Lactic acidosis, a rare and serious form of metabolic acidosis, has been reported with the use of metformin, and metabolic acidosis has been reported with the use of dichlorphenamide. Concurrent use may increase the severity of metabolic acidosis. Measure sodium bicarbonate concentrations at baseline and periodically during dichlorphenamide treatment. If metabolic acidosis occurs or persists, consider reducing the dose or discontinuing dichlorphenamide therapy.
    Dienogest; Estradiol valerate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Diethylstilbestrol, DES: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Dihydrocodeine; Guaifenesin; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Diphenhydramine; Hydrocodone; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Diphenhydramine; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Disopyramide: (Moderate) Disopyramide may enhance the hypoglycemic effects of antidiabetic agents. Patients receiving disopyramide concomitantly with antidiabetic agents should be monitored for changes in glycemic control.
    Dofetilide: (Major) Dofetilide should be co-administered with metformin with caution since both drugs are actively secreted via cationic secretion and could compete for common renal tubular transport systems. This results in a possible increase in plasma concentrations of either drug. Reduced clearance of metformin may increase the risk for lactic acidosis; increased concentrations of dofetilide may increase the risk for side effects including proarrhythmia. Careful patient monitoring and dose adjustment of metformin and dofetilide is recommended.
    Dolutegravir: (Major) Caution is advised when administering dolutegravir with metformin, as coadministration may increase exposure to metformin. Increased exposure to metformin may increase the risk for hypoglycemia, gastrointestinal side effects, and potentially increase the risk for lactic acidosis. If these drugs are used in combination, the total daily dose of metformin must not exceed 1000 mg/day. Close monitoring of blood glucose and patient clinical status is recommended. When stopping dolutegravir, the metformin dose may need to be adjusted. In drug interaction studies, dolutegravir increased both the Cmax and AUC of metformin when metformin was administered at a dose of 500 mg PO twice daily. Dolutegravir inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k]).
    Dolutegravir; Rilpivirine: (Major) Caution is advised when administering dolutegravir with metformin, as coadministration may increase exposure to metformin. Increased exposure to metformin may increase the risk for hypoglycemia, gastrointestinal side effects, and potentially increase the risk for lactic acidosis. If these drugs are used in combination, the total daily dose of metformin must not exceed 1000 mg/day. Close monitoring of blood glucose and patient clinical status is recommended. When stopping dolutegravir, the metformin dose may need to be adjusted. In drug interaction studies, dolutegravir increased both the Cmax and AUC of metformin when metformin was administered at a dose of 500 mg PO twice daily. Dolutegravir inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k]).
    Donepezil; Memantine: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion (e.g., memantine) may decrease metformin elimination by competing for common renal tubular transport systems. It should be noted that in a pharmacokinetic study in which memantine and glyburide; metformin (Glucovance) were coadministered, the pharmacokinetics of memantine, metformin, or glyburide were not altered. Regardless, careful patient monitoring is recommended.
    Doravirine; Lamivudine; Tenofovir disoproxil fumarate: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Drospirenone; Estradiol: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Drospirenone; Ethinyl Estradiol: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Drospirenone; Ethinyl Estradiol; Levomefolate: (Minor) Levomefolate and metformin should be used together cautiously. Plasma concentrations of levomefolate may be reduced during treatment of type 2 diabetes with metformin. Monitor patients for decreased efficacy of levomefolate if these agents are used together. (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Efavirenz; Emtricitabine; Tenofovir: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Efavirenz; Lamivudine; Tenofovir Disoproxil Fumarate: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Emtricitabine: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Emtricitabine; Rilpivirine; Tenofovir alafenamide: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Emtricitabine; Rilpivirine; Tenofovir disoproxil fumarate: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Emtricitabine; Tenofovir alafenamide: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Emtricitabine; Tenofovir disoproxil fumarate: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as emtricitabine, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Enalapril, Enalaprilat: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Enalapril; Felodipine: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Enalapril; Hydrochlorothiazide, HCTZ: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Entecavir: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion (e.g., entecavir) may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Ephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Eprosartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Eprosartan; Hydrochlorothiazide, HCTZ: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Erythromycin; Sulfisoxazole: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Esterified Estrogens: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Esterified Estrogens; Methyltestosterone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estradiol Cypionate; Medroxyprogesterone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estradiol: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estradiol; Levonorgestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estradiol; Norethindrone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estradiol; Norgestimate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estramustine: (Minor) Estramustine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Estramustine may decrease glucose tolerance leading to hyperglycemia.
    Estrogens: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Estropipate: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethacrynic Acid: (Moderate) Loop diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose concentrations.Patients receiving antidiabetic agents should be monitored for changes in blood glucose control if such diuretics are added or deleted. Dosage adjustments may be necessary.
    Ethanol: (Moderate) Patients should be advised to limit their use of ethanol during use of metformin. Blood lactate concentrations and the lactate to pyruvate ratio are increased during excessive (acute or chronic) intake of alcohol with metformin. Elevated lactic acid concentrations are associated with increased morbidity rates as the risk for lactic acidosis is increased. Many non-prescription drug products may be formulated with alcohol; have patients scrutinize product labels prior to consumption. In patients with diabetes, alcohol intake can also cause hypoglycemia or worsen glycemic control as it provides a source of additional calories.
    Ethinyl Estradiol: (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Desogestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Ethynodiol Diacetate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Etonogestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Levonorgestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Levonorgestrel; Ferrous bisglycinate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Levonorgestrel; Folic Acid; Levomefolate: (Minor) Levomefolate and metformin should be used together cautiously. Plasma concentrations of levomefolate may be reduced during treatment of type 2 diabetes with metformin. Monitor patients for decreased efficacy of levomefolate if these agents are used together. (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norelgestromin: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norethindrone Acetate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norethindrone Acetate; Ferrous fumarate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norethindrone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norethindrone; Ferrous fumarate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norgestimate: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethinyl Estradiol; Norgestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Ethotoin: (Minor) Ethotoin and other hydantoins have the potential to increase blood glucose and thus interact with antidiabetic agents pharmacodynamically. Monitor blood glucose for changes in glycemic control. Dosage adjustments may be necessary in some patients.
    Etonogestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Famotidine: (Minor) Famotidine may decrease the renal clearance of metformin secondary to competition for renal tubular transport systems. Such an interaction has been observed when cimetidine was administered with metformin. The decrease in renal excretion led to a 40% increase in metformin AUC. Although interactions with cationic drugs remain theoretical (except for cimetidine), caution is warranted when famotidine and metformin are prescribed concurrently. Famotidine may be less likely to interact with metformin versus cimetidine or ranitidine because of less tubular excretion.
    Famotidine; Ibuprofen: (Minor) Famotidine may decrease the renal clearance of metformin secondary to competition for renal tubular transport systems. Such an interaction has been observed when cimetidine was administered with metformin. The decrease in renal excretion led to a 40% increase in metformin AUC. Although interactions with cationic drugs remain theoretical (except for cimetidine), caution is warranted when famotidine and metformin are prescribed concurrently. Famotidine may be less likely to interact with metformin versus cimetidine or ranitidine because of less tubular excretion.
    Fenofibrate: (Moderate) Dose reductions and increased frequency of glucose monitoring may be required when antidiabetic agents are administered with fibric acid derivatives (e.g., clofibrate, fenofibric acid, fenofibrate, gemfibrozil). Fibric acid derivatives may enhance the hypoglycemic effects of antidiabetic agents through increased insulin sensitivity and decreased glucagon secretion.
    Fenofibric Acid: (Moderate) Dose reductions and increased frequency of glucose monitoring may be required when antidiabetic agents are administered with fibric acid derivatives (e.g., clofibrate, fenofibric acid, fenofibrate, gemfibrozil). Fibric acid derivatives may enhance the hypoglycemic effects of antidiabetic agents through increased insulin sensitivity and decreased glucagon secretion.
    Fexofenadine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Fibric acid derivatives: (Moderate) Dose reductions and increased frequency of glucose monitoring may be required when antidiabetic agents are administered with fibric acid derivatives (e.g., clofibrate, fenofibric acid, fenofibrate, gemfibrozil). Fibric acid derivatives may enhance the hypoglycemic effects of antidiabetic agents through increased insulin sensitivity and decreased glucagon secretion.
    Fluoxetine: (Moderate) In patients with diabetes mellitus, fluoxetine may alter glycemic control. Hypoglycemia has occurred during fluoxetine therapy. Hyperglycemia has developed in patients with diabetes mellitus following discontinuation of the drug. The dosage of insulin and/or other antidiabetic agents may need to be adjusted when therapy with fluoxetine is instituted or discontinued.
    Fluoxetine; Olanzapine: (Moderate) In patients with diabetes mellitus, fluoxetine may alter glycemic control. Hypoglycemia has occurred during fluoxetine therapy. Hyperglycemia has developed in patients with diabetes mellitus following discontinuation of the drug. The dosage of insulin and/or other antidiabetic agents may need to be adjusted when therapy with fluoxetine is instituted or discontinued.
    Fluoxymesterone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Folic Acid, Vitamin B9: (Minor) Levomefolate and metformin should be used together cautiously. Plasma concentrations of levomefolate may be reduced during treatment of type 2 diabetes with metformin. Monitor patients for decreased efficacy of levomefolate if these agents are used together.
    Fosinopril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Fosinopril; Hydrochlorothiazide, HCTZ: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Fosphenytoin: (Minor) Fosphenytoin and other hydantoins have the potential to increase blood glucose and thus interact with antidiabetic agents pharmacodynamically. Monitor blood glucose for changes in glycemic control. Dosage adjustments may be necessary in some patients.
    Furosemide: (Minor) Furosemide may cause hyperglycemia and glycosuria in patients with diabetes mellitus, probably due to diuretic-induced hypokalemia.
    Gadoterate meglumine: (Severe) Metformin and combination products containing metformin should be temporarily discontinued prior to the administration of iodinated contrast media. Metformin should be held for at least 48 hours after contrast administration and not restarted until renal function returns to normal post-procedure. Lactic acidosis has been reported in patients taking metformin that experience nephrotoxicity after use of iodinated contrast media.
    Garlic, Allium sativum: (Moderate) Patients receiving antidiabetic agents should use dietary supplements of Garlic, Allium sativum with caution. Constituents in garlic might have some antidiabetic activity, and may increase serum insulin levels and increase glycogen storage in the liver. Monitor blood glucose and glycemic control. Patients with diabetes should inform their health care professionals of their intent to ingest garlic dietary supplements. Some patients may require adjustment to their hypoglycemic medications over time. One study stated that additional garlic supplementation (0.05 to 1.5 grams PO per day) contributed to improved blood glucose control in patients with type 2 diabetes mellitus within 1 to 2 weeks, and had positive effects on total cholesterol and high/low density lipoprotein regulation over time. It is unclear if hemoglobin A1C is improved or if improvements are sustained with continued treatment beyond 24 weeks. Other reviews suggest that garlic may provide modest improvements in blood lipids, but few studies demonstrate decreases in blood glucose in diabetic and non-diabetic patients. More controlled trials are needed to discern if garlic has an effect on blood glucose in patients with diabetes. When garlic is used in foods or as a seasoning, or at doses of 50 mg/day or less, it is unlikely that blood glucose levels are affected to any clinically significant degree.
    Gemfibrozil: (Moderate) Dose reductions and increased frequency of glucose monitoring may be required when antidiabetic agents are administered with fibric acid derivatives (e.g., clofibrate, fenofibric acid, fenofibrate, gemfibrozil). Fibric acid derivatives may enhance the hypoglycemic effects of antidiabetic agents through increased insulin sensitivity and decreased glucagon secretion.
    Gemifloxacin: (Moderate) Hyperglycemia and hypoglycemia have been reported in patients treated concomitantly with quinolones and antidiabetic agents. Rare cases of severe hypoglycemia have been reported with concomitant use of quinolones and glyburide. Therefore, careful monitoring of blood glucose is recommended when gemifloxacin and antidiabetic agents are coadministered.
    Glimepiride: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glimepiride; Pioglitazone: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glimepiride; Rosiglitazone: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glipizide: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glipizide; Metformin: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glyburide: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glyburide; Metformin: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Glycopyrrolate: (Moderate) Coadministration of glycopyrrolate with metformin my increase metformin plasma concentrations, which may lead to increased metformin effects and possible adverse events. If coadministration is necessary, monitor clinical response to metformin and adjust metformin dose accordingly.
    Glycopyrrolate; Formoterol: (Moderate) Coadministration of glycopyrrolate with metformin my increase metformin plasma concentrations, which may lead to increased metformin effects and possible adverse events. If coadministration is necessary, monitor clinical response to metformin and adjust metformin dose accordingly.
    Green Tea: (Moderate) Green tea catechins have been shown to decrease serum glucose concentrations in vitro. Patients with diabetes mellitus taking antidiabetic agents should be monitored closely for hypoglycemia if consuming green tea products.
    Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Guaifenesin; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Guaifenesin; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Hydralazine; Hydrochlorothiazide, HCTZ: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Irbesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Lisinopril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Losartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Methyldopa: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Metoprolol: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Moexipril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Olmesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Propranolol: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Quinapril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Spironolactone: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Telmisartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Triamterene: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrochlorothiazide, HCTZ; Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Hydrocodone; Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Hydrocodone; Potassium Guaiacolsulfonate; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Hydrocodone; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Hydroxychloroquine: (Major) Careful monitoring of blood glucose is recommended when hydroxychloroquine and antidiabetic agents, including metformin, are coadministered. A decreased dose of the antidiabetic agent may be necessary as severe hypoglycemia has been reported in patients treated concomitantly with hydroxychloroquine and an antidiabetic agent.
    Hydroxyprogesterone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Ibuprofen; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Indacaterol; Glycopyrrolate: (Moderate) Coadministration of glycopyrrolate with metformin my increase metformin plasma concentrations, which may lead to increased metformin effects and possible adverse events. If coadministration is necessary, monitor clinical response to metformin and adjust metformin dose accordingly.
    Indapamide: (Moderate) A potential pharmacodynamic interaction exists between indapamide and antidiabetic agents, like metformin. Indapamide can decrease insulin sensitivity thereby leading to glucose intolerance and hyperglycemia. Diuretic-induced hypokalemia may also lead to hyperglycemia.
    Insulin Aspart: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Aspart; Insulin Aspart Protamine: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Degludec: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Degludec; Liraglutide: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Detemir: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Glargine: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Glargine; Lixisenatide: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Glulisine: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Lispro: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin Lispro; Insulin Lispro Protamine: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulin, Inhaled: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Insulins: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Iodipamide Meglumine: (Severe) Metformin and combination products containing metformin should be temporarily discontinued prior to the administration of iodinated contrast media. Metformin should be held for at least 48 hours after contrast administration and not restarted until renal function returns to normal post-procedure. Lactic acidosis has been reported in patients taking metformin that experience nephrotoxicity after use of iodinated contrast media.
    Ionic Contrast Media: (Severe) Metformin and combination products containing metformin should be temporarily discontinued prior to the administration of iodinated contrast media. Metformin should be held for at least 48 hours after contrast administration and not restarted until renal function returns to normal post-procedure. Lactic acidosis has been reported in patients taking metformin that experience nephrotoxicity after use of iodinated contrast media.
    Ioxaglate Meglumine; Ioxaglate Sodium: (Severe) Metformin and combination products containing metformin should be temporarily discontinued prior to the administration of iodinated contrast media. Metformin should be held for at least 48 hours after contrast administration and not restarted until renal function returns to normal post-procedure. Lactic acidosis has been reported in patients taking metformin that experience nephrotoxicity after use of iodinated contrast media.
    Irbesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Isoniazid, INH: (Minor) Isoniazid, INH may increase blood sugar. Patients receiving antidiabetic agents should be closely monitored for loss of diabetic control when this drug is initiated.
    Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Minor) Isoniazid, INH may increase blood sugar. Patients receiving antidiabetic agents should be closely monitored for loss of diabetic control when this drug is initiated.
    Isoniazid, INH; Rifampin: (Minor) Isoniazid, INH may increase blood sugar. Patients receiving antidiabetic agents should be closely monitored for loss of diabetic control when this drug is initiated.
    Isophane Insulin (NPH): (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Lamivudine, 3TC: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems.
    Lamivudine, 3TC; Zidovudine, ZDV: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems.
    Lamivudine; Tenofovir Disoproxil Fumarate: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, such as lamivudine, may decrease metformin elimination by competing for common renal tubular transport systems. (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Lamotrigine: (Moderate) Coadministration of metformin and lamotrigine may decrease metformin clearance, resulting in increased plasma concentrations and the potential for adverse events, including hypoglycemia. Lamotrigine is an inhibitor of renal tubular secretion via organic cationic transporter 2 (OCT2) proteins, and metformin is excreted via this route.
    Lanreotide: (Moderate) Monitor blood glucose levels regularly in patients with diabetes, especially when lanreotide treatment is initiated or when the dose is altered. Adjust treatment with antidiabetic agents as clinically indicated. Lanreotide inhibits the secretion of insulin and glucagon. Patients treated with lanreotide may experience either hypoglycemia or hyperglycemia.
    Lente Insulin: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Leuprolide; Norethindrone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Levocarnitine: (Moderate) Chromium dietary supplements may lower blood glucose. As part of the glucose tolerance factor molecule, chromium appears to facilitate the binding of insulin to insulin receptors in tissues and to aid in glucose metabolism. Because blood glucose may be lowered by the use of chromium, patients who are on antidiabetic agents may need dose adjustments. Close monitoring of blood glucose is recommended.
    Levofloxacin: (Moderate) Careful monitoring of blood glucose is recommended when levofloxacin and antidiabetic agents, including metformin, are coadministered. Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones and an antidiabetic agent.
    Levomefolate: (Minor) Levomefolate and metformin should be used together cautiously. Plasma concentrations of levomefolate may be reduced during treatment of type 2 diabetes with metformin. Monitor patients for decreased efficacy of levomefolate if these agents are used together.
    Levomefolate; Mecobalamin; Pyridoxal-5-phosphate: (Minor) Levomefolate and metformin should be used together cautiously. Plasma concentrations of levomefolate may be reduced during treatment of type 2 diabetes with metformin. Monitor patients for decreased efficacy of levomefolate if these agents are used together.
    Levonorgestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Levothyroxine: (Minor) Addition of thyroid hormones to metformin may result in increased dosage requirements of metformin. Monitor blood sugars carefully when thyroid therapy is added, discontinued or doses changed.
    Levothyroxine; Liothyronine (Porcine): (Minor) Addition of thyroid hormones to metformin may result in increased dosage requirements of metformin. Monitor blood sugars carefully when thyroid therapy is added, discontinued or doses changed.
    Levothyroxine; Liothyronine (Synthetic): (Minor) Addition of thyroid hormones to metformin may result in increased dosage requirements of metformin. Monitor blood sugars carefully when thyroid therapy is added, discontinued or doses changed.
    Linezolid: (Moderate) Hypoglycemia, including symptomatic episodes, has been noted in post-marketing reports with linezolid in patients with diabetes mellitus receiving therapy with antidiabetic agents, such as insulin and oral hypoglycemic agents. Diabetic patients should be monitored for potential hypoglycemic reactions while on linezolid. If hypoglycemia occurs, discontinue or decrease the dose of the antidiabetic agent or discontinue the linezolid therapy. Linezolid is a reversible, nonselective MAO inhibitor and other MAO inhibitors have been associated with hypoglycemic episodes in diabetic patients receiving insulin or oral hypoglycemic agents.
    Liothyronine: (Minor) Addition of thyroid hormones to metformin may result in increased dosage requirements of metformin. Monitor blood sugars carefully when thyroid therapy is added, discontinued or doses changed.
    Lisdexamfetamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Lisinopril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Lithium: (Moderate) Lithium may cause variable effects on glycemic control when used in patients receiving antidiabetic agents. Monitor blood glucose concentrations closely if lithium is coadministered with antidiabetic agents. Dosage adjustments of antidiabetic agents may be necessary.
    Lomefloxacin: (Moderate) Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones and an antidiabetic agent. Therefore, careful monitoring of blood glucose is recommended when quinolones and antidiabetic agents are co-administered.
    Loratadine; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Lorcaserin: (Moderate) In general, weight reduction may increase the risk of hypoglycemia in patients with type 2 diabetes mellitus treated with antidiabetic agents, such as insulin and/or insulin secretagogues (e.g., sulfonylureas). In clinical trials, lorcaserin use was associated with reports of hypoglycemia. Blood glucose monitoring is warranted in patients with type 2 diabetes prior to starting and during lorcaserin treatment. Dosage adjustments of anti-diabetic medications should be considered. If a patient develops hypoglycemia during treatment, adjust anti-diabetic drug regimen accordingly. Of note, lorcaserin has not been studied in combination with insulin.
    Losartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Lovastatin; Niacin: (Moderate) Niacin (nicotinic acid) interferes with glucose metabolism and can result in hyperglycemia. Changes in glycemic control can usually be corrected through modification of hypoglycemic therapy. Monitor patients taking antidiabetic agents for changes in glycemic control if niacin (nicotinic acid) is added or deleted to the medication regimen. Dosage adjustments may be necessary.
    Mecasermin rinfabate: (Moderate) Use caution in combining mecasermin, recombinant, rh-IGF-1 or mecasermin rinfabate (rh-IGF-1/rh-IGFBP-3) with antidiabetic agents. Patients should be advised to eat within 20 minutes of mecasermin administration. Glucose monitoring is important when initializing or adjusting mecasermin therapies, when adjusting concomitant antidiabetic therapy, and in the event of hypoglycemic symptoms. An increased risk for hypoglycemia is possible. The hypoglycemic effect induced by IGF-1 activity may be exacerbated. The amino acid sequence of mecasermin (rh-IGF-1) is approximately 50 percent homologous to insulin and cross binding with either receptor is possible. Treatment with mecasermin has been shown to improve insulin sensitivity and to improve glycemic control in patients with either Type 1 or Type 2 diabetes mellitus when used alone or in conjunction with insulins.
    Mecasermin, Recombinant, rh-IGF-1: (Moderate) Use caution in combining mecasermin, recombinant, rh-IGF-1 or mecasermin rinfabate (rh-IGF-1/rh-IGFBP-3) with antidiabetic agents. Patients should be advised to eat within 20 minutes of mecasermin administration. Glucose monitoring is important when initializing or adjusting mecasermin therapies, when adjusting concomitant antidiabetic therapy, and in the event of hypoglycemic symptoms. An increased risk for hypoglycemia is possible. The hypoglycemic effect induced by IGF-1 activity may be exacerbated. The amino acid sequence of mecasermin (rh-IGF-1) is approximately 50 percent homologous to insulin and cross binding with either receptor is possible. Treatment with mecasermin has been shown to improve insulin sensitivity and to improve glycemic control in patients with either Type 1 or Type 2 diabetes mellitus when used alone or in conjunction with insulins.
    Medroxyprogesterone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Megestrol: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Meglitinides: (Moderate) Use of metformin with a meglitinide ("glinide") may increase the risk of hypoglycemia. Meglitinides are insulin secretagogues and are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the meglitinide may be needed. Monitor blood sugar.
    Memantine: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion (e.g., memantine) may decrease metformin elimination by competing for common renal tubular transport systems. It should be noted that in a pharmacokinetic study in which memantine and glyburide; metformin (Glucovance) were coadministered, the pharmacokinetics of memantine, metformin, or glyburide were not altered. Regardless, careful patient monitoring is recommended.
    Meperidine; Promethazine: (Minor) Promethazine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Phenothiazines have been reported to increase blood glucose concentrations.
    Mestranol; Norethindrone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance. (Minor) Patients receiving antidiabetic agents should be periodically monitored for changes in glycemic control when hormone therapy is instituted or discontinued. Estrogens can decrease the hypoglycemic effects of antidiabetic agents by impairing glucose tolerance. Changes in glucose tolerance occur more commonly in patients receiving 50 mcg or more of ethinyl estradiol (or equivalent) per day in combined oral contraceptives (COCs), which are not commonly used in practice since the marketing of lower dose COCs, patches, injections and rings. The presence or absence of a concomitant progestin may influence the significance of any hormonal effect on glucose homeostasis.
    Metformin; Repaglinide: (Moderate) Use of metformin with a meglitinide ("glinide") may increase the risk of hypoglycemia. Meglitinides are insulin secretagogues and are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the meglitinide may be needed. Monitor blood sugar.
    Methamphetamine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Methazolamide: (Moderate) Carbonic anhydrase inhibitors may alter blood sugar. Both hyperglycemia and hypoglycemia have been described in patients treated with acetazolamide, and similar effects may be noted with methazolamide. This should be taken into consideration in patients with impaired glucose tolerance or diabetes mellitus who are receiving antidiabetic agents. Monitor blood glucose and for changes in glycemic control and be alert for evidence of an interaction. Carbonic anhydrase inhibitors frequently decrease serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. Use these drugs with caution in patients treated with metformin, as the risk of lactic acidosis may increase. Monitor electrolytes and renal function.
    Methyclothiazide: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Methyltestosterone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Metoclopramide: (Moderate) Because metoclopramide can enhance gastric emptying in diabetic patients, blood glucose can be affected, which, in turn, may affect the clinical response to antidiabetic agents. The dosing of metformin may require adjustment in patients who receive metoclopramide concomitantly.
    Metolazone: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Metyrapone: (Moderate) In patients taking insulin or other antidiabetic agents, the signs and symptoms of acute metyrapone toxicity (e.g., symptoms of acute adrenal insufficiency) may be aggravated or modified.
    Midodrine: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion, like midodrine, may decrease metformin elimination by competing for common renal tubular transport systems. Careful patient monitoring and dose adjustment of metformin and/or midodrine is recommended.
    Moexipril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Monoamine oxidase inhibitors: (Moderate) Animal data indicate that monoamine oxidase inhibitors (MAO inhibitors) may stimulate insulin secretion. Inhibitors of MAO type A have been shown to prolong the hypoglycemic response to insulin and oral sulfonylureas. Serum glucose should be monitored closely when MAOI-type medications, including the selective MAO-B inhibitor selegiline, are added to any regimen containing antidiabetic agents. Although at low doses selegiline is selective for MAO type B, in doses above 30 to 40 mg/day, this selectivity is lost.
    Moxifloxacin: (Moderate) Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones and an antidiabetic agent. Monitor blood glucose when quinolones and antidiabetic agents are coadministered.
    Nandrolone Decanoate: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Naproxen; Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Nateglinide: (Moderate) Use of metformin with a meglitinide ("glinide") may increase the risk of hypoglycemia. Meglitinides are insulin secretagogues and are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the meglitinide may be needed. Monitor blood sugar.
    Nebivolol; Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Niacin, Niacinamide: (Moderate) Niacin (nicotinic acid) interferes with glucose metabolism and can result in hyperglycemia. Changes in glycemic control can usually be corrected through modification of hypoglycemic therapy. Monitor patients taking antidiabetic agents for changes in glycemic control if niacin (nicotinic acid) is added or deleted to the medication regimen. Dosage adjustments may be necessary.
    Niacin; Simvastatin: (Moderate) Niacin (nicotinic acid) interferes with glucose metabolism and can result in hyperglycemia. Changes in glycemic control can usually be corrected through modification of hypoglycemic therapy. Monitor patients taking antidiabetic agents for changes in glycemic control if niacin (nicotinic acid) is added or deleted to the medication regimen. Dosage adjustments may be necessary.
    Nicotine: (Minor) Blood glucose concentrations should be monitored more closely whenever a change in either nicotine intake or smoking status occurs; dosage adjustments of metformin may be needed. Nicotine may increase plasma glucose; tobacco smoking is known to aggravate insulin resistance. The cessation of nicotine therapy or tobacco smoking may result in a decrease in blood glucose.
    Nifedipine: (Minor) Nifedipine may increase the plasma metformin Cmax and AUC and increase the amount of metformin excreted in the urine. Metformin half-life is unaffected. Nifedipine appears to enhance the absorption of metformin.
    Non-Ionic Contrast Media: (Severe) Metformin and combination products containing metformin should be temporarily discontinued prior to the administration of iodinated radiopaque contrast agents. Metformin should be held for at least 48 hours after contrast administration and not restarted until renal function returns to normal post-procedure. Lactic acidosis has been reported in patients taking metformin that experience nephrotoxicity after iodinated contrast media.
    Norethindrone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Norfloxacin: (Moderate) Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones like norfloxacin and an antidiabetic agent like metformin. Monitor blood glucose when norfloxacin and metformin are coadministered.
    Norgestrel: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Octreotide: (Moderate) Monitor patients receiving octreotide concomitantly with insulin or other antidiabetic agents for changes in glycemic control and adjust doses of these medications accordingly. Octreotide alters the balance between the counter-regulatory hormones of insulin, glucagon, and growth hormone, which may result in hypoglycemia or hyperglycemia. The hypoglycemia or hyperglycemia which occurs during octreotide acetate therapy is usually mild, but may result in overt diabetes mellitus or necessitate dose changes in insulin or other hypoglycemic agents. In patients with concomitant type1 diabetes mellitus, octreotide is likely to affect glucose regulation, and insulin requirements may be reduced. Symptomatic hypoglycemia, which may be severe, has been reported in type 1 diabetic patients. In Type 2 diabetes patients with partially intact insulin reserves, octreotide administration may result in decreases in plasma insulin levels and hyperglycemia.
    Ofloxacin: (Moderate) Hyperglycemia and hypoglycemia have been reported in patients treated concomitantly with quinolones and antidiabetic agents. Therefore, careful monitoring of blood glucose is recommended when quinolones and antidiabetic agents are coadministered.
    Olmesartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Ombitasvir; Paritaprevir; Ritonavir: (Major) While no dosage adjustment of metformin is recommended in patients with normal hepatic or renal function, careful patient monitoring and dose adjustment of metformin and/or the potentially interfering drug is recommended with concurrent use. Monitor for signs of onset of lactic acidosis such as respiratory distress, somnolence, and non-specific abdominal distress or worsening renal function. Do not use metformin with paritaprevir in patients with renal insufficiency or hepatic impairment. Drugs that interfere with common renal tubular transport systems involved in the renal elimination of metformin could increase systemic exposure to metformin and may increase the risk for lactic acidosis. Paritaprevir is an inhibitor of the organic anion transporters OATP1B1 and OATP1B3. While initial drug-drug interaction studies of paritaprevir-containing hepatitis treatments have not noted an effect on metformin concentrations, more study is needed.
    Orlistat: (Minor) Weight-loss may affect glycemic control in patients with diabetes mellitus. In many patients, glycemic control may improve. A reduction in dose of oral hypoglycemic medications may be required in some patients taking orlistat. Monitor blood glucose and glycemic control and adjust therapy as clinically indicated.
    Oxandrolone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Oxymetholone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Pasireotide: (Moderate) Monitor blood glucose levels regularly in patients with diabetes, especially when pasireotide treatment is initiated or when the dose is altered. Adjust treatment with antidiabetic agents as clinically indicated. Pasireotide inhibits the secretion of insulin and glucagon. Patients treated with pasireotide may experience either hypoglycemia or hyperglycemia.
    Pegvisomant: (Moderate) Monitor blood glucose levels regularly in patients with diabetes, especially when pegvisomant treatment is initiated or when the dose is altered. Adjust treatment with antidiabetic agents as clinically indicated. Pegvisomant increases sensitivity to insulin by lowering the activity of growth hormone, and in some patients glucose tolerance improves with treatment. Patients with diabetes treated with pegvisomant and antidiabetic agents may be more likely to experience hypoglycemia.
    Pentamidine: (Moderate) Pentamidine can be harmful to pancreatic cells. This effect may lead to hypoglycemia acutely, followed by hyperglycemia with prolonged pentamidine therapy. Patients on antidiabetic agents should be monitored for the need for dosage adjustments during the use of pentamidine.
    Pentoxifylline: (Moderate) Pentoxiphylline has been used concurrently with antidiabetic agents without observed problems, but it may enhance the hypoglycemic action of antidiabetic agents. Patients should be monitored for changes in glycemic control while receiving pentoxifylline in combination with antidiabetic agents.
    Perindopril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Perindopril; Amlodipine: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Phenothiazines: (Minor) Phenothiazines, especially chlorpromazine, may increase blood glucose concentrations. Hyperglycemia and glycosuria have been reported. Patients who are taking antidiabetic agents should monitor for worsening glycemic control when a phenothiazine is instituted.
    Phentermine; Topiramate: (Major) Concurrent use of topiramate and metformin is contraindicated in patients with metabolic acidosis. Topiramate frequently causes metabolic acidosis, a condition for which the use of metformin is contraindicated. During a drug interaction study evaluating concurrent use of topiramate and metformin in healthy volunteers, the following changes in metformin pharmacokinetics were observed: the mean Cmax was increased by 17%, the mean AUC was increased by 25%, and the oral plasma clearance was decreased by 20%. The oral plasma clearance of topiramate was reduced, but the extent of the change is unknown.
    Phenylephrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Phenylephrine; Promethazine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes. (Minor) Promethazine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Phenothiazines have been reported to increase blood glucose concentrations.
    Phenytoin: (Minor) Phenytoin and other hydantoins have the potential to increase blood glucose and thus interact with antidiabetic agents pharmacodynamically. Monitor blood glucose for changes in glycemic control. Dosage adjustments may be necessary in some patients.
    Prasterone, Dehydroepiandrosterone, DHEA (Dietary Supplements): (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Prasterone, Dehydroepiandrosterone, DHEA (FDA-approved): (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Progesterone: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Progestins: (Minor) Patients receiving antidiabetic agents like metformin should be closely monitored for signs indicating changes in diabetic control when therapy with progestins is instituted or discontinued. Progestins can impair glucose tolerance.
    Promethazine: (Minor) Promethazine should be used cautiously in patients receiving metformin. Patients should routinely monitor their blood glucose as indicated. Phenothiazines have been reported to increase blood glucose concentrations.
    Propantheline: (Moderate) Propantheline slows GI motility, which may increase the absorption of metformin from the small intestine. A 19% increase in metformin AUC has been reported in studies of this interaction in healthy volunteers. However, no serious side effects resulted.
    Propoxyphene: (Moderate) Propoxyphene may enhance the hypoglycemic action of antidiabetic agents. Patients should be closely monitored for changes in glycemic control while receiving propoxyphene in combination with antidiabetic agents.
    Protease inhibitors: (Moderate) New onset diabetes mellitus, exacerbation of diabetes mellitus, and hyperglycemia due to insulin resistance have been reported with use of anti-retroviral protease inhibitors. Another possible mechanism is impairment of beta-cell function. Onset averaged approximately 63 days after initiating protease inhibitor therapy, but has occurred as early as 4 days after beginning therapy. Diabetic ketoacidosis has occurred in some patients including patients who were not diabetic prior to protease inhibitor treatment. Patients taking antidiabetic therapy should be closely monitored for changes in glycemic control, specifically hyperglycemia, if protease inhibitor therapy is initiated.
    Pseudoephedrine: (Moderate) Sympathomimetic agents and adrenergic agonists tend to increase blood glucose concentrations when administered systemically. Monitor for loss of glycemic control when pseudoephedrine, phenylephrine, and other sympathomimetics are administered to patients taking antidiabetic agents. Epinephrine and other sympathomimetics, through stimulation of alpha- and beta- receptors, increase hepatic glucose production and glycogenolysis and inhibit insulin secretion. Also, adrenergic medications may decrease glucose uptake by muscle cells. For treatment of cold symptoms, nasal decongestants may be preferable for short term, limited use (1 to 3 days) as an alternative to systemic decongestants in patients taking medications for diabetes.
    Pyrimethamine; Sulfadoxine: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Quinapril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Ramipril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Ranolazine: (Major) Limit the dose of metformin to 1700 mg/day if coadministered with ranolazine 1000 mg twice daily. Coadministration of metformin and ranolazine 1000 mg twice daily results in increased plasma concentrations of metformin. Monitor blood glucose concentrations, for common metformin side effects such as gastrointestinal complaints. There is potential for an increased risk for lactic acidosis, which is associated with high metformin concentrations. Doses of metformin do not require reduction if coadministered with ranolazine 500 mg twice daily, as metformin exposure was not significantly increased when coadministered with this lower dose of ranolazine. Ranolazine inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k]).
    Regular Insulin: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Regular Insulin; Isophane Insulin (NPH): (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Repaglinide: (Moderate) Use of metformin with a meglitinide ("glinide") may increase the risk of hypoglycemia. Meglitinides are insulin secretagogues and are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the meglitinide may be needed. Monitor blood sugar.
    Reserpine: (Moderate) Reserpine may mask the signs and symptoms of hypoglycemia. Patients receiving these drugs concomitantly should be monitored for changes in glycemic control.
    Sacubitril; Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Salicylates: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control.
    Somatropin, rh-GH: (Moderate) Patients with diabetes mellitus should be monitored closely during somatropin (recombinant rhGH) therapy. Antidiabetic drugs (e.g., insulin or oral agents) may require adjustment when somatropin therapy is instituted in these patients. Growth hormones, such as somatropin, may decrease insulin sensitivity, leading to glucose intolerance and loss of blood glucose control. Therefore, glucose levels should be monitored periodically in all patients treated with somatropin, especially in those with risk factors for diabetes mellitus.
    Sparfloxacin: (Moderate) Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with quinolones like sparfloxacin and an antidiabetic agent like metformin. Monitor blood glucose when sparfloxacin and metformin are coadministered.
    Sulfadiazine: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Sulfamethoxazole; Trimethoprim, SMX-TMP, Cotrimoxazole: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Sulfasalazine: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Sulfisoxazole: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Sulfonamides: (Moderate) Sulfonamides may enhance the hypoglycemic action of antidiabetic agents; patients with diabetes mellitus should be closely monitored during sulfonamide treatment. Sulfonamides may induce hypoglycemia in some patients by increasing the secretion of insulin from the pancreas. Patients at risk include those with compromised renal function, those fasting for prolonged periods, those that are malnourished, and those receiving high or excessive doses of sulfonamides.
    Sulfonylureas: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Tacrolimus: (Moderate) Tacrolimus has been reported to cause hyperglycemia. Furthermore, tacrolimus has been implicated in causing insulin-dependent diabetes mellitus in patients after renal transplantation. Tacrolimus may have direct beta-cell toxicity. Patients should be monitored for worsening of glycemic control if Tacrolimus is initiated in patients receiving antidiabetic agents.
    Tegaserod: (Moderate) Because tegaserod can enhance gastric emptying in diabetic patients, blood glucose can be affected, which, in turn, may affect the clinical response to antidiabetic agents. The dosing of antidiabetic agents may require adjustment in patients who receive GI prokinetic agents concomitantly.
    Telmisartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Tenofovir Alafenamide: (Moderate) According to the manufacturer, interactions are not expected when metformin is administered with tenofovir alafenamide; however, because tenofovir and metformin can compete for elimination through the kidneys, use of these medications together may increase the risk for side effects, such as lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir alafenamide, may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Tenofovir, PMPA: (Moderate) Certain medications used concomitantly with metformin may increase the risk of lactic acidosis. Drugs that are eliminated by renal tubular secretion, such as tenofovir, PMPA may decrease metformin elimination by competing for common renal tubular transport systems. Although such interactions remain theoretical, careful patient monitoring and dose adjustment of metformin and/or the interfering cationic drug are recommended.
    Testolactone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Testosterone: (Moderate) Changes in insulin sensitivity or glycemic control may occur in patients treated with androgens. In diabetic patients, the metabolic effects of androgens may decrease blood glucose and, therefore, may decrease antidiabetic agent dosage requirements. Moniitor blood glucose and HbA1C when these drugs are used together.
    Thiazide diuretics: (Moderate) Thiazide diuretics can decrease the hypoglycemic effects of antidiabetic agents by producing an increase in blood glucose levels. It appears that the effects of thiazide diuretics on glycemic control are dose-related and low doses can be instituted without deleterious effects on glycemic control. In addition, thiazide diuretics reduce the risk of stroke and cardiovascular disease in patients with diabetes. Patients receiving metformin should be monitored for changes in blood glucose control if any of these diuretics are added or deleted. Dosage adjustments may be necessary.
    Thyroid hormones: (Minor) Addition of thyroid hormones to metformin may result in increased dosage requirements of metformin. Monitor blood sugars carefully when thyroid therapy is added, discontinued or doses changed.
    Tobacco: (Minor) Tobacco smoking is known to aggravate insulin resistance. The cessation of tobacco smoking may result in a decrease in blood glucose. Blood glucose concentrations should be monitored more closely whenever a change in either smoking status occurs; dosage adjustments in antidiabetic agents may be needed.
    Tolazamide: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Tolbutamide: (Moderate) Use of metformin with a sulfonylurea may increase the risk of hypoglycemia. Sulfonylureas are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of the sulfonylurea may be needed. Monitor blood sugar.
    Topiramate: (Major) Concurrent use of topiramate and metformin is contraindicated in patients with metabolic acidosis. Topiramate frequently causes metabolic acidosis, a condition for which the use of metformin is contraindicated. During a drug interaction study evaluating concurrent use of topiramate and metformin in healthy volunteers, the following changes in metformin pharmacokinetics were observed: the mean Cmax was increased by 17%, the mean AUC was increased by 25%, and the oral plasma clearance was decreased by 20%. The oral plasma clearance of topiramate was reduced, but the extent of the change is unknown.
    Torsemide: (Minor) Hyperglycemia has been detected during torsemide therapy, but the incidence is low. Because of this, a potential pharmacodynamic interaction exists between torsemide and all antidiabetic agents, including metformin. Monitor blood glucose.
    Trandolapril: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Trandolapril; Verapamil: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Trospium: (Moderate) Trospium, if used concomitantly with metformin, may increase the risk of lactic acidosis. Cationic drugs that are eliminated by renal tubular secretion like trospium may decrease metformin elimination by competing for common renal tubular transport systems.
    Ultralente Insulin: (Moderate) Coadministration of metformin with an insulin may increase the risk of hypoglycemia. Insulins are known to cause hypoglycemia. To manage hypoglycemic risk, lower doses of insulin may be needed. Monitor blood sugar and adjust insulin dosage as clinically indicated.
    Valsartan: (Moderate) Angiotensin II receptor antagonists (ARBs) may enhance the hypoglycemic effects of metformin by improving insulin sensitivity. In addition, angiotensin II receptor antagonists have been associated with a reduced incidence in the development of new-onset diabetes in patients with hypertension or other cardiac disease. ARBs may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Vandetanib: (Moderate) Vandetanib inhibits renal elimination of metformin. Increased metformin exposure may lead to hypoglycemia and an increased risk for metformin related side effects, such as hypoglycemia, gastrointestinal complaints, or an increased risk for lactic acidosis. Caution is advised. Carefully monitor the patient. Dosage adjustment of metformin may be necessary. Coadministration with vandetanib increased the Cmax and AUC of metformin by 50% and 74%, respectively. Vandetanib inhibits common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k]).
    Zonisamide: (Moderate) Zonisamide frequently decreases serum bicarbonate and induces non-anion gap, hyperchloremic metabolic acidosis. Use zonisamide with caution in patients treated with metformin, as the risk of lactic acidosis may increase.

    PREGNANCY AND LACTATION

    Pregnancy

    Premenopausal anovulatory females with insulin resistance (i.e., those with polycystic ovary syndrome (PCOS)) may resume ovulation as a result of metformin therapy; patients may be at risk of conception if adequate contraception is not used in those not desiring to become pregnant. In some cases, metformin is used as an adjunct in PCOS patients to regulate menstrual cycles or to enhance fertility. Metformin is not recommended for routine use during pregnancy. Metformin does pass through the placenta and the fetus is likely exposed to therapeutic concentrations of metformin. The American College of Obstetricians and Gynecologists (ACOG) and the American Diabetes Association (ADA) continue to recommend human insulin as the standard of care in women with gestational diabetes mellitus (GDM) requiring medical therapy. Per ACOG, in women who decline insulin therapy or are unable to safely administer insulin, metformin is the preferred second-line choice. Per the ADA, metformin may be used to treat GDM as a treatment option; however, no long term safety data are available for any oral agent. Metformin may cause a lower risk of neonatal hypoglycemia and less maternal weight gain than insulin; however, some data suggest that metformin may slightly increase the risk of prematurity. The ADA notes that in some clinical studies, nearly 50% of GDM patients initially treated with metformin have needed the addition of insulin in order to achieve acceptable glucose control. Many studies and analyses of metformin in use in pregnancy have been published. Data suggest no increase in the rates of expected birth defects or other adverse outcomes in exposed infants and studies comparing metformin to insulin in the treatment of gestational diabetes have generally found no significant differences in glycemic control or pregnancy outcomes.

    MECHANISM OF ACTION

    Mechanism of Action: Metformin is an antihyperglycemic agent that improves glucose tolerance, lowering both basal and postprandial plasma glucose with mechanisms different from other classes of oral antidiabetic agents. Metformin decreases hepatic gluconeogenesis production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. With metformin therapy, insulin secretion remains unchanged while fasting insulin levels and day-long plasma insulin response may actually decrease. Metformin improve glucose utilization in skeletal muscle and adipose tissue by increasing cell membrane glucose transport. This effect may be due to improved binding of insulin to insulin receptors since metformin is not effective in diabetics without some residual functioning pancreatic islet cells. Unlike the sulfonylureas, metformin rarely causes hypoglycemia since it does not significantly change insulin concentrations. An important distinction is that sulfonylureas increase insulin secretion thus making them useful in non-obese patients with type 2 diabetes while metformin improves insulin resistance, a common pathophysiologic finding in obese patients with type 2 diabetes. Metformin causes a 10—20% decrease in fatty-acid oxidation and a slight increase in glucose oxidation. Unlike phenformin, metformin does not inhibit the mitochondrial oxidation of lactate unless plasma concentrations of metformin become excessive (i.e., in patients with renal failure) and/or hypoxia is present.Clinically, metformin lowers fasting and postprandial hyperglycemia. The decrease in fasting plasma glucose is approximately 25—30%. Unlike oral sulfonylureas, metformin rarely causes hypoglycemia. Thus, metformin demonstrates more of an antihyperglycemic action than a hypoglycemic action. Metformin does not cause weight gain and in fact, may cause a modest weight loss due to drug-induced anorexia. Metformin also decreases plasma VLDL triglycerides resulting in modest decreases in plasma triglycerides and total cholesterol. Patients receiving metformin show a significant improvement in hemoglobin A1c, and a tendency toward improvement in the lipid profile, especially when baseline values are abnormally elevated.Insulin resistance is a primary cause of polycystic ovarian syndrome (PCOS). In PCOS patients, metformin reduces insulin resistance and lowers insulin levels, which lowers serum androgen concentrations, restores normal menstrual cycles and ovulation, and may help to resolve PCOS-associated infertility. Metformin, when administered to lean, overweight, and moderately obese women with PCOS, has been found to significantly reduce serum leuteinizing hormone (LH) and increase follicle stimulating hormone (FSH) and sex hormone binding globulin (SHBG). Serum testosterone concentrations were also found to decrease by approximately 50%.

    PHARMACOKINETICS

    Metformin is administered orally. The drug is distributed rapidly into peripheral body tissues and fluids and appears to distribute slowly into erythrocytes and to a deep tissue compartment (most likely GI tissues). The highest concentrations are found in the GI tract (10 times the concentrations in the plasma) and lower concentrations in the kidney, liver, and salivary gland tissue. Metformin does not bind to hepatic or plasma proteins. Metformin is not metabolized by the liver and this fact may explain why the risk of lactic acidosis is much less for metformin than for phenformin (i.e., approximately 10% of patients have an inherited defect in the ability to metabolize phenformin). The drug is excreted by the kidneys, largely unchanged, through an active tubular process. Tubular secretion may be altered by many cationic drugs. Approximately 10% of an oral dose is excreted in the feces, presumably as unabsorbed metformin and about 90% of a dose is excreted by the kidneys within 24 hours. Although the average elimination half-life in the plasma is 6.2 hours in patients with normal renal function, metformin is distributed to and accumulates in red blood cells, which leads to a much longer elimination half-life in the blood (17.6 hours).
     
    Affected cytochrome P450 (CYP450) isoenzymes and drug transporters: Organic cationic transporter-2 (OCT2), multidrug and toxin extrusion (MATE1 and MATE2k)
    Drugs that interfere with common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2]/multidrug and toxin extrusion [MATE1 and MATE2k] inhibitors such as ranolazine, vandetanib, dolutegravir, and cimetidine) increase systemic exposure to metformin. Careful patient monitoring and dose adjustment of metformin and/or the potentially interfering drug is recommended with concurrent use.

    Oral Route

    Metformin Solution (Riomet): The rate and extent of absorption is comparable to regular-release tablets. Peak plasma concentrations are achieved at approximately 2.2 hours. The extent of absorption from the oral solution increases when given with food, and while there is a negligible decrease in Cmax, the Tmax increases from 2.5 to approximately 4 hours. Studies indicate that dose proportionality is lacking with increasing doses due to a decrease in the absorption at higher doses.
    Metformin Regular-release tablets: The bioavailability of 500 mg tablets is 50% to 60% with peak plasma concentrations achieved at approximately 2.5 hours. Food decreases the extent and slightly delays the absorption. Studies indicate that dose proportionality is lacking with increasing doses due to a decrease in the oral absorption at higher doses.
    Metformin Extended-release tablets (Glucophage XR): Using a dual hydrophilic polymer system, metformin is released slowly by diffusion through a gel matrix, allowing for once-daily administration. Peak plasma concentrations are achieved at approximately 7 hours (range, 4 to 8 hours). While peak plasma concentrations are approximately 20% lower for extended-release tablets versus the same dose of regular-release tablets, the extent of absorption from 2,000 mg once-daily of extended- release tablets is similar to the same total daily dose administered as 1,000 mg twice-daily of regular-release tablets. Food increases the extent of absorption of extended-release tablets (as per AUC) by approximately 50%, although Cmax and Tmax are unaltered.
    Metformin Extended-release tablets (Fortamet): Using single-composition osmotic technology (SCOT), metformin is released at a constant rate from an osmotically active tablet core surrounded by a semi-permeable membrane. Peak plasma concentrations are achieved at approximately 6 hours (range 3 to 10 hours). While peak concentrations are higher with Fortamet, the bioavailability of Fortamet 2,000 mg once daily in the evening (as per AUC) is similar to the same total daily dose administered as regular-release tablets 1,000 mg twice daily. When administered with food, the extent of absorption is increased by approximately 60%; in addition, Cmax is increased by 30% and Tmax is prolonged (6.1 hours vs. 4 hours). There is a dose-proportional increase in exposure following administration of 1,000 to 2,500 mg.
    Metformin Extended-release tablets (Glumetza): Using gastric-retentive (GR) technology, tablets are designed to remain in the stomach and deliver metformin to the upper GI tract to enhance absorption over an extended period of time, thus allowing for once-daily dosing. Glumetza tablets must be administered directly after a meal to maximize therapeutic benefit. Peak plasma concentrations from Glumetza 1,000 mg after a meal are achieved in 7 to 8 hours. In single and multiple dose studies, once daily Glumetza 1,000 mg provides equivalent systemic exposure (as per AUC), and up to 35% higher Cmax concentrations, when compared to 500 mg twice daily regular-release tablets. Low-fat and high-fat meals increase systemic exposure (as per AUC) by 38% and 73%, respectively, relative to fasting. Both meal types prolong Tmax by approximately 3 hours, but Cmax is not affected.