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  • CLASSES

    Cystic Fibrosis Agents

    DEA CLASS

    Rx

    DESCRIPTION

    Cystic fibrosis transmembrane conductance regulator (CFTR) modulator
    Used for treatment of CF in patients who are homozygous for F508del mutation or who have at least 1 mutation in CFTR gene responsive to tezacaftor; ivacaftor based on in vitro data and/or clinical evidence
    Liver function monitoring required at baseline and periodically throughout therapy

    COMMON BRAND NAMES

    Symdeko

    HOW SUPPLIED

    Symdeko Oral Tab: 150-100-150mg, 75-50-75mg

    DOSAGE & INDICATIONS

    For the treatment of cystic fibrosis (CF) in patients who are homozygous for the F508del mutation or have at least 1 mutation in the CFTR gene that is responsive to tezacaftor; ivacaftor.
    Oral dosage
    Adults

    1 tablet (containing tezacaftor 100 mg/ivacaftor 150 mg) PO in the morning and 1 tablet (containing ivacaftor 150 mg) PO in the evening, approximately 12 hours apart and given with fat-containing food. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.

    Children and Adolescents 12 to 17 years

    1 tablet (containing tezacaftor 100 mg/ivacaftor 150 mg) PO in the morning and 1 tablet (containing ivacaftor 150 mg) PO in the evening, approximately 12 hours apart and given with fat-containing food. Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.

    Children 6 to 11 years weighing 30 kg or more

    1 tablet (containing tezacaftor 100 mg/ivacaftor 150 mg) PO in the morning and 1 tablet (containing ivacaftor 150 mg) PO in the evening, approximately 12 hours apart and given with fat-containing food.[62870] Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.

    Children 6 to 11 years weighing less than 30 kg

    1 tablet (containing tezacaftor 50 mg/ivacaftor 75 mg) PO in the morning and 1 tablet (containing ivacaftor 75 mg) PO in the evening, approximately 12 hours apart and given with fat-containing food.[62870] Coadministration of certain drugs may need to be avoided or dosage adjustments may be necessary; review drug interactions.

    MAXIMUM DOSAGE

    Adults

    1 tablet (tezacaftor 100 mg; ivacaftor 150 mg) and 1 tablet (ivacaftor 150 mg) per day (total daily dose: tezacaftor 100 mg/ivacaftor 300 mg).

    Geriatric

    1 tablet (tezacaftor 100 mg; ivacaftor 150 mg) and 1 tablet (ivacaftor 150 mg) per day (total daily dose: tezacaftor 100 mg/ivacaftor 300 mg).

    Adolescents

    1 tablet (tezacaftor 100 mg; ivacaftor 150 mg) and 1 tablet (ivacaftor 150 mg) per day (total daily dose: tezacaftor 100 mg/ivacaftor 300 mg).

    Children

    12 years: 1 tablet (tezacaftor 100 mg; ivacaftor 150 mg) and 1 tablet (ivacaftor 150 mg) per day (total daily dose: tezacaftor 100 mg/ivacaftor 300 mg).
    6 to 11 years weighing 30 kg or more: 1 tablet (tezacaftor 100 mg; ivacaftor 150 mg) and 1 tablet (ivacaftor 150 mg) per day (total daily dose: tezacaftor 100 mg/ivacaftor 300 mg).
    6 to 11 years weighing less than 30 kg: 1 tablet (tezacaftor 50 mg; ivacaftor 75 mg) and 1 tablet (ivacaftor 75 mg) per day (total daily dose: tezacaftor 50 mg/ivacaftor 150 mg).
    1 to 5 years: Safety and efficacy have not been established.

    Infants

    Safety and efficacy have not been established.

    Neonates

    Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    Mild impairment (Child-Pugh Class A): No dosage adjustment necessary.
     
    Moderate impairment (Child-Pugh Class B):
    6 to 11 years weighing 30 kg or more and 12 years and older: 1 tablet containing tezacaftor 100 mg/ivacaftor 150 mg PO once daily; NO ivacaftor 150 mg dose.
    6 to 11 years weighing less than 30 kg: 1 tablet containing tezacaftor 50 mg/ivacaftor 75 mg PO once daily; NO ivacaftor 75 mg dose.
     
    Severe impairment (Child-Pugh Class C):
    6 to 11 years weighing 30 kg or more and 12 years and older: 1 tablet containing tezacaftor 100 mg/ivacaftor 150 mg PO once daily (or less frequently); NO ivacaftor 150 mg dose. Use with caution; this drug has not been studied in patients with severe hepatic impairment.
    6 to 11 years weighing less than 30 kg: 1 tablet containing tezacaftor 50 mg/ivacaftor 75 mg PO once daily (or less frequently); NO ivacaftor 75 mg dose. Use with caution; this drug has not been studied in patients with severe hepatic impairment.[62870]

    Renal Impairment

    CrCl more than 30 mL/minute: No dosage adjustment necessary.
    CrCl 30 mL/minute or less: Use with caution; specific guidelines for dosage adjustment are not available.

    ADMINISTRATION

    Oral Administration
    Oral Solid Formulations

    Swallow tablets whole.
    Administer each dose with fat-containing food (e.g., eggs, butter, nuts, peanut butter, cheese pizza, whole-milk dairy products).
    For a missed dose, if 6 hours or less have passed since the time the drug is usually taken, take the dose as soon as possible and then resume the normal schedule. If more than 6 hours have passed, the missed dose should NOT be taken and the patient should resume the usual dosing schedule.

    STORAGE

    Symdeko:
    - Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F

    CONTRAINDICATIONS / PRECAUTIONS

    General Information

    If a patient's genotype is unknown, an FDA-cleared CF mutation test should be used to detect the presence of a CFTR mutation followed by verification with bi-directional sequencing when recommended by the mutation test instructions for use.

    Hepatic disease

    Use tezacaftor; ivacaftor with caution in patients with hepatic disease; elevated transaminases have been observed. Dosage reduction is recommended in patients with moderate to severe hepatic impairment (Child-Pugh Class B or C). Monitor ALT and AST prior to initiation, every 3 months during the first year of treatment, and annually thereafter. Consider more frequent monitoring in patients with a history of transaminase elevations. If significant elevations (e.g., ALT/AST more than 5 times the upper limit of normal [ULN] or ALT/AST more than 3 times ULN with bilirubin more than 2 times ULN) occur, interrupt dosing and closely monitor laboratory tests until abnormalities resolve. Upon resolution, consider the benefits and risks before resuming treatment.

    Renal disease, renal failure, renal impairment

    Use tezacaftor; ivacaftor with caution in patients with severe renal impairment, renal failure, or end stage renal disease. Tezacaftor; ivacaftor has not been studied in patients with moderate to severe renal impairment.

    Cataracts, children

    Cases of non-congenital lens opacities/cataracts have been reported in pediatric patients treated with tezacaftor; ivacaftor as well as ivacaftor monotherapy. Although other risk factors (e.g., corticosteroid use, radiation exposure) were present in some cases, a possible risk attributable to tezacaftor; ivacaftor cannot be excluded. Baseline and follow-up ophthalmological examinations are recommended for children and adolescents initiating tezacaftor; ivacaftor treatment.

    Pregnancy

    There are limited and incomplete human data from clinical trials and postmarketing reports on the use of tezacaftor; ivacaftor during human pregnancy to inform a drug-associated risk. Separate oral administration of tezacaftor and ivacaftor was not found to be teratogenic or result in adverse developmental effects in animals at doses approximately 0.2 to 3 times and 4 to 16 times the maximum recommended human dose (MRHD), respectively. No adequate and well-controlled studies have been performed in pregnant women.

    Breast-feeding

    There is no information regarding the presence of tezacaftor or ivacaftor in human milk, the effects on the breast-feeding infant, or the effects on milk production. Both tezacaftor and ivacaftor are excreted into the breast milk of lactating rats; however, due to species-specific differences in lactation physiology, animal lactation data may not reliably predict levels in human milk. No studies have been done to assess the effects of tezacaftor; ivacaftor on a nursing infant. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    ADVERSE REACTIONS

    Moderate

    elevated hepatic enzymes / Delayed / Incidence not known

    Mild

    headache / Early / 15.0-15.0
    nausea / Early / 9.0-9.0
    dizziness / Early / 4.0-4.0
    nasal congestion / Early / 4.0-4.0

    DRUG INTERACTIONS

    Acetaminophen; Caffeine; Dihydrocodeine: (Moderate) Concomitant use of dihydrocodeine with ivacaftor may increase dihydrocodeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased dihydromorphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of dihydrocodeine until stable drug effects are achieved. Discontinuation of ivacaftor could decrease dihydrocodeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to dihydrocodeine. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Ivacaftor is a weak inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of dihydrocodeine.
    Acetaminophen; Diphenhydramine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Acetaminophen; Hydrocodone: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Acetaminophen; Oxycodone: (Moderate) Consider a reduced dose of oxycodone with frequent monitoring for respiratory depression and sedation if concurrent use of ivacaftor is necessary. If ivacaftor is discontinued, consider increasing the oxycodone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Oxycodone is a CYP3A4 substrate, and coadministration with a weak inhibitor like ivacaftor can increase oxycodone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of oxycodone. If ivacaftor is discontinued, oxycodone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to oxycodone.
    Acetaminophen; Tramadol: (Minor) Use caution when administering ivacaftor and tramadol concurrently. Ivacaftor is an inhibitor of CYP3A and tramadol is partially metabolized by CYP3A. Co-administration can theoretically increase tramadol exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Afatinib: (Moderate) If the concomitant use of ivacaftor and afatinib is necessary, consider reducing the afatinib dose by 10 mg per day if the original dose is not tolerated; resume the previous dose of afatinib as tolerated after discontinuation of ivacaftor. Afatinib is a P-glycoprotein (P-gp) substrate and inhibitor in vitro. Ivacaftor and its M1 metabolite are weak P-gp inhibitors; coadministration may increase plasma concentrations of afatinib. Coadministration of ivacaftor with digoxin, a sensitive P-gp substrate, increased digoxin exposure by 1.3-fold. Administration of another P-gp inhibitor, ritonavir (200 mg twice daily for 3 days), 1 hour before afatinib (single dose) increased the afatinib AUC and Cmax by 48% and 39%, respectively; there was no change in the afatinib AUC when ritonavir was administered at the same time as afatinib or 6 hours later. In healthy subjects, the relative bioavailability for AUC and Cmax of afatinib was 119% and 104%, respectively, when coadministered with ritonavir, and 111% and 105% when ritonavir was administered 6 hours after afatinib. The manufacturer of afatinib recommends permanent discontinuation of therapy for severe or intolerant adverse drug reactions at a dose of 20 mg per day, but does not address a minimum dose otherwise.
    Alfentanil: (Moderate) Use caution when administering ivacaftor and alfentanil concurrently. Ivacaftor is an inhibitor of CYP3A, and alfentanil is a CYP3A substrate. Co-administration can increase alfentanil exposure leading to increased or prolonged therapeutic effects and adverse events.
    Alprazolam: (Moderate) Use caution when administering ivacaftor and alprazolam concurrently because patients are at increased risk for adverse effects from alprazolam. Ivacaftor is a CYP3A inhibitor, and alprazolam is a CYP3A substrate. Co-administration of ivacaftor with midazolam, another CYP3A substrate, increased midazolam exposure by 1.5-fold.
    Amiodarone: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with amiodarone; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor combination tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); amiodarone is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If amiodarone and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and amiodarone is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Amoxicillin; Clarithromycin; Lansoprazole: (Major) If clarithromycin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and clarithromycin is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with clarithromycin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); clarithromycin is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Amoxicillin; Clarithromycin; Omeprazole: (Major) If clarithromycin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and clarithromycin is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with clarithromycin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); clarithromycin is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Apalutamide: (Major) Coadministration of ivacaftor with apalutamide is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and apalutamide is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and apalutamide together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of apalutamide, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%. Tezacaftor exposures can also be expected to decrease significantly during coadministration with strong CYP3A inducers.
    Aprepitant, Fosaprepitant: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with a 3 day oral regimen of aprepitant; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor combination tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); aprepitant is a moderate CYP3A inhibitor when administered as a 3 day oral regimen (single oral and IV fosaprepitant doses have not been shown to alter concentrations of CYP3A substrates). Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If multi-day regimens of aprepitant and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate, and aprepitant, when administered as a 3-day oral regimen (125 mg/80 mg/80 mg), is a moderate CYP3A4 inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold. When administered as a single oral or single intravenous dose, the inhibitory effect of aprepitant on CYP3A4 is weak and did not result in a clinically significant increase in the AUC of a sensitive substrate.
    Aspirin, ASA; Caffeine; Dihydrocodeine: (Moderate) Concomitant use of dihydrocodeine with ivacaftor may increase dihydrocodeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased dihydromorphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of dihydrocodeine until stable drug effects are achieved. Discontinuation of ivacaftor could decrease dihydrocodeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to dihydrocodeine. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Ivacaftor is a weak inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of dihydrocodeine.
    Aspirin, ASA; Oxycodone: (Moderate) Consider a reduced dose of oxycodone with frequent monitoring for respiratory depression and sedation if concurrent use of ivacaftor is necessary. If ivacaftor is discontinued, consider increasing the oxycodone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Oxycodone is a CYP3A4 substrate, and coadministration with a weak inhibitor like ivacaftor can increase oxycodone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of oxycodone. If ivacaftor is discontinued, oxycodone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to oxycodone.
    Atazanavir: (Major) If atazanavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and atazanavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with atazanavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); atazanavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Atazanavir; Cobicistat: (Major) If atazanavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and atazanavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) If cobicistat and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and cobicistat is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with atazanavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); atazanavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with cobicistat; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); cobicistat is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Atropine; Hyoscyamine; Phenobarbital; Scopolamine: (Major) Coadministration of ivacaftor with phenobarbital is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and phenobarbital is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. Additionally, phenobarbital is a CYP2C9 substrate and ivacaftor may inhibit CYP2C9. Coadministration may increase exposure to phenobarbital leading to increased or prolonged therapeutic effects and adverse events. (Major) Do not administer tezacaftor; ivacaftor and phenobarbital together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of phenobarbital, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Belladonna Alkaloids; Ergotamine; Phenobarbital: (Major) Coadministration of ivacaftor with phenobarbital is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and phenobarbital is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. Additionally, phenobarbital is a CYP2C9 substrate and ivacaftor may inhibit CYP2C9. Coadministration may increase exposure to phenobarbital leading to increased or prolonged therapeutic effects and adverse events. (Major) Do not administer tezacaftor; ivacaftor and phenobarbital together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of phenobarbital, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%. (Moderate) Use caution when administering ivacaftor and ergotamine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as ergotamine, can increase ergotamine exposure leading to increased or prolonged therapeutic effects and adverse events, including the risk for ergot toxicity.
    Benzhydrocodone; Acetaminophen: (Moderate) Concurrent use of benzhydrocodone with ivacaftor may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Consider a dose reduction of benzhydrocodone until stable drug effects are achieved. Monitor patients for respiratory depression and sedation at frequent intervals. Discontinuation of ivacaftor in a patient taking benzhydrocodone may decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Benzhydrocodone is a prodrug for hydrocodone. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Betrixaban: (Major) Avoid betrixaban use in patients with severe renal impairment receiving ivacaftor. Reduce betrixaban dosage to 80 mg PO once followed by 40 mg PO once daily in all other patients receiving ivacaftor. Bleeding risk may be increased; monitor patients closely for signs and symptoms of bleeding. Betrixaban is a substrate of P-gp; ivacaftor inhibits P-gp.
    Bexarotene: (Moderate) Use caution when administering ivacaftor and bexarotene concurrently; the clinical impact of this interaction has not yet been determined. Administration of ivacaftor with strong CYP3A inducers is not recommended because sub-therapeutic ivacaftor exposure could result. Ivacaftor is a CYP3A substrate and bexarotene is a moderate CYP3A inducer. Co-administration with a strong CYP3A inducer decreased the ivacaftor exposure by approximately 9-fold.
    Boceprevir: (Major) If boceprevir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly (e.g., if the usual dosage is 150 mg twice daily, reduce to 150 mg twice weekly). Ivacaftor is a CYP3A substrate, and boceprevir is a strong CYP3A inhibitor. Coadministration with ketoconazole, another strong CYP3A inhibitor, increased ivacaftor exposure by 8.5-fold. Ivacaftor is also an inhibitor of CYP3A and P-glycoprotein (P-gp); boceprevir is metabolized by CYP3A4 and is a substrate of P-gp. Coadministration may increase boceprevir exposure leading to increased or prolonged therapeutic effects and adverse events.
    Brigatinib: (Moderate) Monitor for a decrease in the efficacy of ivacaftor if coadministration with brigatinib is necessary. Ivacaftor is a sensitive CYP3A4 substrate. At clinically relevant concentrations, brigatinib induced CYP3A via activation of the pregnane X receptor (PXR); this may decrease concentrations of sensitive CYP3A substrates.
    Brompheniramine; Guaifenesin; Hydrocodone: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Budesonide: (Moderate) Use caution when administering ivacaftor and budesonide concurrently. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as budesonide, can increase budesonide exposure leading to increased or prolonged therapeutic effects and adverse events.
    Budesonide; Formoterol: (Moderate) Use caution when administering ivacaftor and budesonide concurrently. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as budesonide, can increase budesonide exposure leading to increased or prolonged therapeutic effects and adverse events.
    Buprenorphine: (Moderate) Use caution when administering ivacaftor and buprenorphine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as buprenorphine, can increase buprenorphine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Buprenorphine; Naloxone: (Moderate) Use caution when administering ivacaftor and buprenorphine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as buprenorphine, can increase buprenorphine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Caffeine; Ergotamine: (Moderate) Use caution when administering ivacaftor and ergotamine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as ergotamine, can increase ergotamine exposure leading to increased or prolonged therapeutic effects and adverse events, including the risk for ergot toxicity.
    Candesartan: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as candesartan. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Candesartan; Hydrochlorothiazide, HCTZ: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as candesartan. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Carbamazepine: (Major) Coadministration of ivacaftor with carbamazepine is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and carbamazepine is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and carbamazepine together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of carbamazepine, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Carbetapentane; Diphenhydramine; Phenylephrine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Carvedilol: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as carvedilol. Ivacaftor is an inhibitor of CYP3A, P-glycoprotein (Pgp) and a weak inhibitor of CYP2C9; carvedilol is partially metabolized by CYP3A, CYP2C9 and is a substrate of Pgp. Co-administration of ivacaftor with CYP3A, CYP2C9, and Pgp substrates,such as carvedilol, can theoretically increase carvedilol exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Celecoxib: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as celecoxib. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Ceritinib: (Major) If ceritinib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ceritinib is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ceritinib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, give one tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ceritinib is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Chloramphenicol: (Major) If chloramphenicol and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and chloramphenicol is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with chloramphenicol; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); chloramphenicol is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Moderate) Concomitant use of dihydrocodeine with ivacaftor may increase dihydrocodeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased dihydromorphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of dihydrocodeine until stable drug effects are achieved. Discontinuation of ivacaftor could decrease dihydrocodeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to dihydrocodeine. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Ivacaftor is a weak inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of dihydrocodeine.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Moderate) Concomitant use of dihydrocodeine with ivacaftor may increase dihydrocodeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased dihydromorphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of dihydrocodeine until stable drug effects are achieved. Discontinuation of ivacaftor could decrease dihydrocodeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to dihydrocodeine. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Ivacaftor is a weak inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of dihydrocodeine.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Chlorpheniramine; Hydrocodone: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Chlorpheniramine; Hydrocodone; Phenylephrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Chlorpheniramine; Hydrocodone; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Ciprofloxacin: (Moderate) Monitor patients closely for tezacaftor; ivacaftor-related adverse reactions if coadministration with ciprofloxacin is necessary. Pharmacokinetic data suggest that no dose adjustment is necessary if tezacaftor; ivacaftor is coadministered with ciprofloxacin. However, because ciprofloxacin is a moderate CYP3A inhibitor, there is a potential for increased tezacaftor; ivacaftor exposure and adverse reactions with concurrent use of ciprofloxacin. Of note, FDA-approved labeling generally recommends tezacaftor; ivacaftor dosage adjustment when coadministered with a moderate CYP3A inhibitor (1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days).
    Clarithromycin: (Major) If clarithromycin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and clarithromycin is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with clarithromycin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); clarithromycin is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Clozapine: (Moderate) Use caution when administering ivacaftor and clozapine concurrently. Ivacaftor is an inhibitor of CYP3A and clozapine is partially metabolized by CYP3A. Treatment with clozapine has been associated with QT prolongation, torsade de pointes (TdP), cardiac arrest, and sudden death. Elevated plasma concentrations of clozapine occurring through CYP inhibition may potentially increase the risk of life-threatening arrhythmias, sedation, anticholinergic effects, seizures, orthostasis, or other adverse effects. According to the manufacturer, patients receiving clozapine in combination with an inhibitor of CYP3A4 should be monitored for adverse reactions. Consideration should be given to reducing the clozapine dose if necessary. If the inhibitor is discontinued after dose adjustments are made, monitor for lack of clozapine effectiveness and consider increasing the clozapine dose if necessary.
    Cobicistat: (Major) If cobicistat and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and cobicistat is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with cobicistat; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); cobicistat is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Colchicine: (Major) Use caution when administering ivacaftor and colchicine concurrently; increased monitoring and/or dose adjustment of colchine may be necessary. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as colchicine, can increase colchicine exposure leading to increased or prolonged therapeutic effects and adverse events. Fatal colchicine toxicity has been reported when given with strong CYP3A4 and Pgp inhibitors.
    Colchicine; Probenecid: (Major) Use caution when administering ivacaftor and colchicine concurrently; increased monitoring and/or dose adjustment of colchine may be necessary. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as colchicine, can increase colchicine exposure leading to increased or prolonged therapeutic effects and adverse events. Fatal colchicine toxicity has been reported when given with strong CYP3A4 and Pgp inhibitors.
    Conivaptan: (Major) Avoid concomitant use of conivaptan with tezacaftor; ivacaftor. Subsequent treatment with tezacaftor; ivacaftor may be initiated no sooner than 1 week after the infusion of conivaptan is complete. Conivaptan is a strong CY3A inhibitor; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). (Major) If conivaptan and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and conivaptan is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold.
    Crizotinib: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with crizotinib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); crizotinib is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If crizotinib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and crizotinib is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Cyclosporine: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with cyclosporine; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. In addition, coadministration may increase the systemic exposure of cyclosporine. Appropriate monitoring should be used; adjust the cyclosporine dosage as necessary. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate), ivacaftor is a weak P-gp inhibitor, and cyclosporine is a moderate CYP3A inhibitor and P-gp substrate. (Major) If cyclosporine and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Coadministration may increase exposure to both drugs leading to increased or prolonged therapeutic effects and adverse events. More careful monitoring of cyclosporine blood concentrations may be warranted. Ivacaftor is a CYP3A substrate and cyclosporine is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold. In addition, ivacaftor is an inhibitor of CYP3A and P-glycoprotein (P-gp); cyclosporine is a sensitive CYP3A and P-gp substrate.
    Dabigatran: (Moderate) Increased serum concentrations of dabigatran are possible when dabigatran, a P-glycoprotein (P-gp) substrate, is coadministered with ivacaftor, a mild P-gp inhibitor. Patients should be monitored for increased adverse effects of dabigatran. When dabigatran is administered for treatment or reduction in risk of recurrence of deep venous thrombosis (DVT) or pulmonary embolism (PE) or prophylaxis of DVT or PE following hip replacement surgery, avoid coadministration with P-gp inhibitors like ivacaftor in patients with CrCl less than 50 mL/minute. When dabigatran is used in patients with non-valvular atrial fibrillation andsevere renal impairment (CrCl less than 30 mL/minute), avoid coadministration with ivacaftor, as serum concentrations of dabigatran are expected to be higher than when administered to patients with normal renal function. P-gp inhibition and renal impairment are the major independent factors that result in increased exposure to dabigatran.
    Danazol: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with danazol; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); danazol is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If danazol and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and danazol is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Dapsone: (Major) If dapsone and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and dapsone is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Darunavir: (Major) If darunavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and darunavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with darunavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); darunavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Darunavir; Cobicistat: (Major) If cobicistat and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and cobicistat is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) If darunavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and darunavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with cobicistat; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); cobicistat is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with darunavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); darunavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Major) If cobicistat and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and cobicistat is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) If darunavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and darunavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with cobicistat; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); cobicistat is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with darunavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); darunavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Dasabuvir; Ombitasvir; Paritaprevir; Ritonavir: (Major) If ritonavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ritonavir is a CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ritonavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ritonavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Delavirdine: (Major) If delavirdine and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and delavirdine is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with delavirdine; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor mg should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); delavirdine is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Dextromethorphan; Diphenhydramine; Phenylephrine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Diazepam: (Moderate) Use caution when administering ivacaftor and diazepam concurrently because patients may be at increased risk for adverse effects from diazepam. Ivacaftor is a CYP3A inhibitor, and diazepam is a CYP3A substrate. Diazepam is also metabolized by CYP2C19, which is not affected by ivacaftor. Co-administration of ivacaftor with midazolam, another CYP3A substrate, increased midazolam exposure by 1.5-fold.
    Diclofenac: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with diclofenac. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; diclofenac is metabolized by CYP3A and CYP2C9. Co-administration can theoretically increase diclofenac exposure leading to increased or prolonged therapeutic effects and adverse events. Do not exceed a total daily diclofenac dose of 100 mg.
    Diclofenac; Misoprostol: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with diclofenac. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; diclofenac is metabolized by CYP3A and CYP2C9. Co-administration can theoretically increase diclofenac exposure leading to increased or prolonged therapeutic effects and adverse events. Do not exceed a total daily diclofenac dose of 100 mg.
    Digoxin: (Moderate) Administration of tezacaftor; ivacaftor may increase the systemic exposure of digoxin and increase or prolong the therapeutic effect and adverse reactions. Appropriate monitoring should be used. Digoxin is a sensitive P-gp substrate; ivacaftor is a weak inhibitor of P-gp. Coadministration of tezacaftor; ivacaftor with digoxin increased digoxin exposure by 1.3-fold. (Moderate) Coadministration of ivacaftor with digoxin may increase digoxin exposure leading to increased or prolonged therapeutic effects and adverse events. Digoxin is a substrate for P-glycoprotein (P-gp). Ivacaftor is an inhibitor of P-glycoprotein (P-gp). Use caution when administering ivacaftor and digoxin concurrently.
    Dihydrocodeine; Guaifenesin; Pseudoephedrine: (Moderate) Concomitant use of dihydrocodeine with ivacaftor may increase dihydrocodeine plasma concentrations, resulting in greater metabolism by CYP2D6, increased dihydromorphine concentrations, and prolonged opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of dihydrocodeine until stable drug effects are achieved. Discontinuation of ivacaftor could decrease dihydrocodeine plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to dihydrocodeine. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Ivacaftor is a weak inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of dihydrocodeine.
    Dihydroergotamine: (Moderate) Use caution when administering ivacaftor and dihydroergotamine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as dihydroergotamine, can increase dihydroergotamine exposure leading to increased or prolonged therapeutic effects and adverse events, including the risk for ergot toxicity.
    Diltiazem: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with diltiazem; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); diltiazem is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If diltiazem and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and diltiazem is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Diphenhydramine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Diphenhydramine; Hydrocodone; Phenylephrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4. (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Diphenhydramine; Ibuprofen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined. (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ibuprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Diphenhydramine; Naproxen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined. (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as naproxen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Diphenhydramine; Phenylephrine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as diphenhydramine. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Disopyramide: (Moderate) Use caution when administering ivacaftor and disopyramide concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as disopyramide, can increase disopyramide exposure leading to increased or prolonged therapeutic effects and adverse events.
    Doravirine; Lamivudine; Tenofovir disoproxil fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Doxepin: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as doxepin. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Doxorubicin: (Major) Ivacaftor is a mild inhibitor of CYP3A and P-glycoprotein (P-gp); doxorubicin is a major CYP3A4 and P-gp substrate. Clinically significant interactions have been reported when doxorubicin was coadministered with inhibitors of CYP3A4 and/or P-gp, resulting in increased concentration and clinical effect of doxorubicin. Avoid coadministration of ivacaftor and doxorubicin if possible. If avoidance is not possible, closely monitor for increased side effects of doxorubicin including myelosuppression and cardiotoxicity.
    Dronabinol: (Minor) Use caution if coadministration of dronabinol with ivacaftor is necessary, and monitor for an increase in dronabinol-related adverse reactions (e.g., feeling high, dizziness, confusion, somnolence). Dronabinol is a CYP2C9 and 3A4 substrate; ivacaftor is a weak inhibitor of CYP3A4 and a weak CYP2C9 inhibitor in vitro. Concomitant use may result in elevated plasma concentrations of dronabinol.
    Dronedarone: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with dronedarone; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); dronedarone is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If dronedarone and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and dronedarone is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Duvelisib: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with duvelisib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); duvelisib is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) Administer ivacaftor at the usual recommended dose but reduce the frequency to once daily if coadministered with duvelisib. Ivacaftor is a sensitive CYP3A substrate and duvelisib is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Efavirenz; Emtricitabine; Tenofovir: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Efavirenz; Lamivudine; Tenofovir Disoproxil Fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Eletriptan: (Moderate) Use caution when administering ivacaftor and eletriptan concurrently. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as eletriptan, can increase eletriptan exposure leading to increased or prolonged therapeutic effects and adverse events.
    Eliglustat: (Major) In poor CYP2D6 metabolizers (PMs), coadministration of ivacaftor and eliglustat is not recommended. In extensive CYP2D6 metabolizers (EM) with mild hepatic impairment, coadministration of these agents requires dosage reduction of eliglustat to 84 mg PO once daily. Ivacaftor and its primary metabolite M1 are considered weak CYP3A inhibitors; eliglustat is a CYP3A and CYP2D6 substrate. Because CYP3A plays a significant role in the metabolism of eliglustat in CYP2D6 PMs, coadministration of eliglustat with CYP3A inhibitors may increase eliglustat exposure and the risk of serious adverse events (e.g., QT prolongation and cardiac arrhythmias) in these patients.
    Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Alafenamide: (Major) If cobicistat and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and cobicistat is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with cobicistat; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); cobicistat is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) If cobicistat and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and cobicistat is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with cobicistat; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor/ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); cobicistat is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively. (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Emtricitabine; Rilpivirine; Tenofovir disoproxil fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Emtricitabine; Tenofovir disoproxil fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Enalapril; Felodipine: (Moderate) Use caution when administering ivacaftor and felodipine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as felodipine, can increase felodipine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Encorafenib: (Major) Coadministration of encorafenib with ivacaftor may result in increased toxicity or decreased efficacy of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate. In vitro studies with encorafenib showed time-dependent inhibition of CYP3A4 and induction of CYP3A4. The clinical relevance of the in vivo effect of encorafenib on CYP3A4 is not established.
    Enzalutamide: (Major) Coadministration of ivacaftor with enzalutamide is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a CYP3A4 substrate and enzalutamide is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and enzalutamide together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of enzalutamide, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Ergotamine: (Moderate) Use caution when administering ivacaftor and ergotamine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as ergotamine, can increase ergotamine exposure leading to increased or prolonged therapeutic effects and adverse events, including the risk for ergot toxicity.
    Erythromycin: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with erythromycin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); erythromycin is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If erythromcyin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and erythromcyin is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Erythromycin; Sulfisoxazole: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with erythromycin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); erythromycin is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If erythromcyin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and erythromcyin is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Esomeprazole; Naproxen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as naproxen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Estazolam: (Moderate) Use caution when administering ivacaftor and estazolam concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as estazolam, can increase estazolam exposure leading to increased or prolonged therapeutic effects and adverse events.
    Everolimus: (Moderate) Administration of tezacaftor; ivacaftor may increase the systemic exposure of everolimus. Appropriate monitoring should be used; adjust everolimus dosage as necessary. Everolimus is a P-gp substrate; ivacaftor is a weak inhibitor of P-gp. (Moderate) Monitor for increased everolimus adverse reactions if coadministered with ivacaftor as concurrent use may increase everolimus exposure. Everolimus is a substrate of CYP3A4 and P-gp with a narrow therapeutic index; ivacaftor is an inhibitor of CYP3A4 and P-gp.
    Ezetimibe; Simvastatin: (Minor) Use caution when administering ivacaftor and simvastatin concurrently. Coadministration of ivacaftor with simvastatin may increase simvastatin exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined. Simvastatin is a sensitive CYP3A4 substrate; ivacaftor is a weak CYP3A4 inhibitor.
    Famotidine; Ibuprofen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ibuprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Fedratinib: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with fedratinib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); fedratinib is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If fedratinib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and fedratinib is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Felodipine: (Moderate) Use caution when administering ivacaftor and felodipine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as felodipine, can increase felodipine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Fentanyl: (Moderate) Use caution when administering ivacaftor and fentanyl concurrently. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as fentanyl, can increase fentanyl exposure leading to increased or prolonged therapeutic effects and adverse events.
    Flibanserin: (Moderate) The concomitant use of flibanserin and multiple weak CYP3A4 inhibitors, including ivacaftor, may increase flibanserin concentrations, which may increase the risk of flibanserin-induced adverse reactions. Therefore, patients should be monitored for hypotension, syncope, somnolence, or other adverse reactions, and the risks of combination therapy with multiple weak CYP3A4 inhibitors and flibanserin should be discussed with the patient.
    Fluconazole: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with fluconazole; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); fluconazole is a moderate CYP3A inhibitor. Coadministration of fluconazole increased ivacaftor exposure 3-fold. Simulation suggests fluconazole may increase tezacaftor exposure 2-fold. (Major) If fluconazole and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate. Coadministration with fluconazole, a moderate CYP3A inhibitor, increased ivacaftor exposure by 3-fold.
    Fluoxetine: (Minor) Although an interaction between ivacaftor and fluoxetine is possible, the clinical impact of this interaction has not yet been determined. Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates. Fluoxetine is partially metabolized by CYP2C9, but it is also a substrate for at least 2 other enzymes. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may possibly lead to increased exposure to fluoxetine; however, because fluoxetine has multiple metabolic pathways, the clinical impact of this inhibition is not clear. In addition, ivacaftor is a CYP3A substrate, and fluoxetine is a mild CYP3A inhibitor. Co-administration may lead to increased ivacaftor exposure.
    Fluoxetine; Olanzapine: (Minor) Although an interaction between ivacaftor and fluoxetine is possible, the clinical impact of this interaction has not yet been determined. Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates. Fluoxetine is partially metabolized by CYP2C9, but it is also a substrate for at least 2 other enzymes. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may possibly lead to increased exposure to fluoxetine; however, because fluoxetine has multiple metabolic pathways, the clinical impact of this inhibition is not clear. In addition, ivacaftor is a CYP3A substrate, and fluoxetine is a mild CYP3A inhibitor. Co-administration may lead to increased ivacaftor exposure.
    Flurbiprofen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as flurbiprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Fluvastatin: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as fluvastatin. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Fluvoxamine: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with fluvoxamine; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); fluvoxamine is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If fluvoxamine and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and fluvoxamine is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Fosamprenavir: (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with fosamprenavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); fosamprenavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively. (Moderate) Use caution when administering ivacaftor and fosamprenavir concurrently; the clinical effect of this interaction is unknown. Ivacaftor is a CYP3A substrate, and fosamprenavir is a CYP3A inhibitor and can also act as an inducer. Co-administration may lead to altered ivacaftor exposure. Ivacaftor is also an inhibitor of CYP3A , CYP2C9, and P-glycoprotein (Pgp); fosamprenavir is metabolized by CYP3A and CYP2C9 and is a substrate of Pgp. Co-administration may increase fosamprenavir exposure leading to increased or prolonged therapeutic effects and adverse events.
    Fosphenytoin: (Major) Coadministration of ivacaftor with fosphenytoin is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and fosphenytoin is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and fosphenytoin together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of fosphenytoin, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Glecaprevir; Pibrentasvir: (Moderate) Caution is advised with the coadministration of glecaprevir and ivacaftor as coadministration may increase serum concentrations of glecaprevir and increase the risk of adverse effects. Glecaprevir is a substrate of P-glycoprotein (P-gp); ivacaftor is a P-gp inhibitor.
    Glimepiride: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glimepiride. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Glimepiride; Pioglitazone: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glimepiride. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Glimepiride; Rosiglitazone: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glimepiride. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Glipizide: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glipizide. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Glipizide; Metformin: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glipizide. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Glyburide: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glyburide. Ivacaftor is an inhibitor of P-glycoprotein (Pgp) and a weak inhibitor of CYP2C9; glyburide is metabolized by CYP2C9 and is substrate of Pgp. Co-administration of ivacaftor with Pgp and CYP2C9 substrates, such as glyburide, can theoretically increase glyburide exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Glyburide; Metformin: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as glyburide. Ivacaftor is an inhibitor of P-glycoprotein (Pgp) and a weak inhibitor of CYP2C9; glyburide is metabolized by CYP2C9 and is substrate of Pgp. Co-administration of ivacaftor with Pgp and CYP2C9 substrates, such as glyburide, can theoretically increase glyburide exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Grapefruit juice: (Major) Avoid food or drink containing grapefruit juice or Seville oranges during treatment with tezacaftor; ivacaftor. Grapefruit contains one or more components that inhibit CYP3A; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). (Major) The manufacturer recommends avoiding grapefruit or Seville oranges during ivacaftor therapy because ivacaftor exposure may be increased. Ivacaftor is a CYP3A substrate. Grapefruit juice and Seville oranges contain components that inhibit CYP3A, and therefore, may reduce ivacaftor metabolism.
    Guaifenesin; Hydrocodone: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Homatropine; Hydrocodone: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Hydrochlorothiazide, HCTZ; Losartan: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as losartan. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; losartan is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates,such as losartan, can theoretically increase losartan exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Hydrocodone: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Hydrocodone; Ibuprofen: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4. (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ibuprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Hydrocodone; Phenylephrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Hydrocodone; Potassium Guaiacolsulfonate: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Hydrocodone; Potassium Guaiacolsulfonate; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Hydrocodone; Pseudoephedrine: (Moderate) Concomitant use of hydrocodone with ivacaftor may increase hydrocodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of hydrocodone until stable drug effects are achieved. Discontinuation of ivacaftor could decrease hydrocodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to hydrocodone. If ivacaftor is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Hydrocodone is a substrate for CYP3A4. Ivacaftor is a weak inhibitor of CYP3A4.
    Ibuprofen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ibuprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Ibuprofen; Oxycodone: (Moderate) Consider a reduced dose of oxycodone with frequent monitoring for respiratory depression and sedation if concurrent use of ivacaftor is necessary. If ivacaftor is discontinued, consider increasing the oxycodone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Oxycodone is a CYP3A4 substrate, and coadministration with a weak inhibitor like ivacaftor can increase oxycodone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of oxycodone. If ivacaftor is discontinued, oxycodone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to oxycodone. (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ibuprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Ibuprofen; Pseudoephedrine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ibuprofen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Idelalisib: (Major) If idelalisib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and idelalisib is a CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with idelalisib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); idelalisib is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Imatinib: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with imatinib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); imatinib is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If imatinib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and imatinib is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Indinavir: (Major) If indinavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and indinavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with indinavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); indinavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Indomethacin: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as indomethacin. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Isavuconazonium: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with isavuconazonium; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); isavuconazonium is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If isavuconazonium and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and isavuconazole, the active moiety of isavuconazonium, is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Major) Coadministration of ivacaftor with rifampin is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and rifampin is a strong CYP3A4 inducer. Coadministration with rifampin significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and rifampin together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of rifampin, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with rifampin decreased ivacaftor exposure 89%.
    Isoniazid, INH; Rifampin: (Major) Coadministration of ivacaftor with rifampin is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and rifampin is a strong CYP3A4 inducer. Coadministration with rifampin significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and rifampin together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of rifampin, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with rifampin decreased ivacaftor exposure 89%.
    Itraconazole: (Major) If itraconazole and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and itraconazole is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with itraconazole; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); itraconazole is a strong CYP3A inhibitor. Coadministration of itraconazole increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Ivosidenib: (Moderate) Monitor for loss of efficacy of ivacaftor during coadministration of ivosidenib; a ivacaftor dose adjustment may be necessary. Ivacaftor is a sensitive substrate of CYP3A4; ivosidenib induces CYP3A4 and may lead to decreased ivacaftor concentrations.
    Ixabepilone: (Moderate) Frequently monitor peripheral blood counts between cycles of ixabepilone, and for other acute ixabepilone-related adverse reactions if coadministration with ivacaftor is necessary; consider the use of an alternative agent to ivacaftor that does not inhibit CYP3A4. Ixabepilone is a CYP3A4 substrate and ivacaftor is a weak CYP3A4 inhibitor. The effect of weak CYP3A4 inhibitors on exposure to ixabepilone has not been studied.
    Ketoconazole: (Major) If ketoconazole and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate. Coadministration with ketoconazole, a strong CYP3A inhibitor, increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ketoconazole; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ketoconazole is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Lamivudine; Tenofovir Disoproxil Fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Lanreotide: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with lanreotide; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); lanreotide is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold.
    Lansoprazole; Naproxen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as naproxen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Lapatinib: (Moderate) Monitor for an increase in lapatinib-related adverse reactions if coadministration with ivacaftor is necessary. Lapatinib is a P-glycoprotein (P-gp) substrate and ivacaftor is a P-gp inhibitor. Increased plasma concentrations of lapatinib are likely.
    Lefamulin: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with oral lefamulin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); oral lefamulin is a moderate CYP3A inhibitor; an interaction is not expected with intravenous lefamulin. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If oral lefamulin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Additionally, monitor for lefamulin-related adverse effects as concurrent use may increase exposure from lefamulin tablets; an interaction is not expected with intravenous lefamulin. Ivacaftor is a CYP3A substrate and P-gp inhibitor. Oral lefamulin is a CYP3A4 and P-gp substrate and moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Letermovir: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with letermovir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); letermovir is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If letermovir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. In patients also receiving cyclosporine, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly, because the magnitude of the interaction may be increased. Ivacaftor is a CYP3A substrate. Letermovir is a moderate CYP3A4 inhibitor; however, when given with cyclosporine, the combined effect on CYP3A4 substrates may be similar to a strong CYP3A4 inhibitor. Coadministration with other moderate and strong CYP3A inhibitors increased ivacaftor exposure by 3- and 8.5-fold, respectively.
    Loperamide: (Moderate) The plasma concentration of loperamide, a P-glycoprotein (P-gp) substrate, may be increased when administered concurrently with ivacaftor, an inhibitor of P-gp. If these drugs are used together, monitor for loperamide-associated adverse reactions, such as CNS effects and cardiac toxicities (i.e., syncope, ventricular tachycardia, QT prolongation, torsade de pointes, cardiac arrest).
    Loperamide; Simethicone: (Moderate) The plasma concentration of loperamide, a P-glycoprotein (P-gp) substrate, may be increased when administered concurrently with ivacaftor, an inhibitor of P-gp. If these drugs are used together, monitor for loperamide-associated adverse reactions, such as CNS effects and cardiac toxicities (i.e., syncope, ventricular tachycardia, QT prolongation, torsade de pointes, cardiac arrest).
    Lopinavir; Ritonavir: (Major) If ritonavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ritonavir is a CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with lopinavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); lopinavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ritonavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ritonavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Losartan: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as losartan. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; losartan is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates,such as losartan, can theoretically increase losartan exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Lovastatin: (Moderate) Monitoring for lovastatin-related adverse events (i.e., myopathy, rhabdomyolysis) is recommended if administered concurrently with ivacaftor. Coadministration can increase lovastatin exposure leading to increased or prolonged therapeutic effects and adverse events. Lovastatin is a CYP3A4 substrate; ivacaftor is a weak CYP3A4 inhibitor.
    Lovastatin; Niacin: (Moderate) Monitoring for lovastatin-related adverse events (i.e., myopathy, rhabdomyolysis) is recommended if administered concurrently with ivacaftor. Coadministration can increase lovastatin exposure leading to increased or prolonged therapeutic effects and adverse events. Lovastatin is a CYP3A4 substrate; ivacaftor is a weak CYP3A4 inhibitor.
    Maraviroc: (Minor) Use caution if coadministration of maraviroc with ivacaftor is necessary, due to a possible increase in maraviroc exposure. Maraviroc is a CYP3A and P-glycoprotein (Pgp) substrate and ivacaftor is a weak CYP3A4/Pgp inhibitor. Monitor for an increase in adverse effects with concomitant use.
    Meloxicam: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as meloxicam. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; meloxicam is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates,such as meloxicam, can theoretically increase meloxicam exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Methadone: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as methadone. Ivacaftor is an inhibitor of CYP3A, P-glycoprotein (Pgp), and a weak inhibitor of CYP2C9; methadone is metabolized by CYP3A4, CYP2C9, and is a substrate of Pgp. Co-administration of ivacaftor with CYP3A, CYP2C9, and Pgp substrates,such as methadone may increase methadone exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Midazolam: (Moderate) Use caution when administering ivacaftor and midazolam concurrently because patients are at increased risk for adverse effects from midazolam. Ivacaftor is a CYP3A inhibitor, and midazolam is a CYP3A substrate. When administered with ivacaftor, midazolam exposure was increased by 1.5-fold.
    Mifepristone: (Major) If mifepristone and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate, and mifepristone is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with mifepristone; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); mifepristone is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Mitotane: (Major) Coadministration of ivacaftor with mitotane is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and mitotane is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and mitotane together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of mitotane, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Morphine: (Moderate) Use caution when administering ivacaftor and morphine concurrently. Ivacaftor is an inhibitor of P-glycoprotein (P-gp). Coadministration of ivacaftor with P-gp substrates, such as morphine, can increase morphine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Morphine; Naltrexone: (Moderate) Use caution when administering ivacaftor and morphine concurrently. Ivacaftor is an inhibitor of P-glycoprotein (P-gp). Coadministration of ivacaftor with P-gp substrates, such as morphine, can increase morphine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Naproxen: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as naproxen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Naproxen; Pseudoephedrine: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as naproxen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Naproxen; Sumatriptan: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as naproxen. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Nateglinide: (Moderate) Monitor blood glucose and for signs of hypoglycemia. Ivacaftor is a weak inhibitor of CYP2C9; nateglinide is metabolized by CYP2C9. Use of ivacaftor with nateglinide can theoretically increase nateglinide exposure leading to increased or prolonged therapeutic effects; however, the clinical impact of this potential interaction has not yet been determined.
    Nefazodone: (Major) If nefazodone and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate, and nefazodone is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with nefazodone; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); nefazodone is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Nelfinavir: (Major) If nelfinavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate, and nelfinavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with nelfinavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); nelfinavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Netupitant, Fosnetupitant; Palonosetron: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with netupitant; palonosetron; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); netupitant is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If netupitant; palonosetron and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and netupitant is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Niacin; Simvastatin: (Minor) Use caution when administering ivacaftor and simvastatin concurrently. Coadministration of ivacaftor with simvastatin may increase simvastatin exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined. Simvastatin is a sensitive CYP3A4 substrate; ivacaftor is a weak CYP3A4 inhibitor.
    Nifedipine: (Moderate) Use caution when administering ivacaftor and nifedipine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as nifedipine, can increase nifedipine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Nilotinib: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with nilotinib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); nilotinib is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If nilotinib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and nilotinib is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Nintedanib: (Moderate) Dual inhibitors of P-glycoprotein (P-gp) and CYP3A4, such as ivacaftor, are expected to increase the exposure and clinical effect of nintedanib. If use together is necessary, closely monitor for increased nintedanib side effects including gastrointestinal toxicity (nausea, vomiting, diarrhea, abdominal pain, loss of appetite), headache, elevated liver enzymes, and hypertension. A dose reduction, interruption of therapy, or discontinuation of nintedanib therapy may be necessary. Ivacaftor is a mild inhibitor of both P-glycoprotein (P-gp) and CYP3A4; nintedanib is a P-gp substrate and a minor CYP3A4 substrate. In drug interactions studies, administration of nintedanib with a dual P-gp and CYP3A4 inhibitor increased nintedanib AUC by 60%.
    Nisoldipine: (Major) Avoid coadministration of nisoldipine with ivacaftor due to increased plasma concentrations of nisoldipine. If coadministration is unavoidable, monitor blood pressure closely during concurrent use of these medications. Nisoldipine is a CYP3A4 substrate and ivacaftor is a CYP3A4 inhibitor.
    Ombitasvir; Paritaprevir; Ritonavir: (Major) If ritonavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ritonavir is a CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ritonavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ritonavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Oxycodone: (Moderate) Consider a reduced dose of oxycodone with frequent monitoring for respiratory depression and sedation if concurrent use of ivacaftor is necessary. If ivacaftor is discontinued, consider increasing the oxycodone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Oxycodone is a CYP3A4 substrate, and coadministration with a weak inhibitor like ivacaftor can increase oxycodone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of oxycodone. If ivacaftor is discontinued, oxycodone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to oxycodone.
    Phenobarbital: (Major) Coadministration of ivacaftor with phenobarbital is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and phenobarbital is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. Additionally, phenobarbital is a CYP2C9 substrate and ivacaftor may inhibit CYP2C9. Coadministration may increase exposure to phenobarbital leading to increased or prolonged therapeutic effects and adverse events. (Major) Do not administer tezacaftor; ivacaftor and phenobarbital together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of phenobarbital, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Phenytoin: (Major) Coadministration of ivacaftor with phenytoin is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and phenytoin is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and phenytoin together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of phenytoin, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Pimozide: (Minor) Use caution when administering ivacaftor and pimozide concurrently. Ivacaftor is an inhibitor of CYP3A and pimozide is partially metabolized by CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as pimozide, can theoretically increase pimozide exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Piroxicam: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as piroxicam. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Posaconazole: (Major) If posaconazole and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate, and posaconazole is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with posaconazole; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); posaconazole is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Prasugrel: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as prasugrel. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; prasugrel is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as prasugrel, can theoretically increase prasugrel exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Prednisolone: (Moderate) Use caution when administering ivacaftor and prednisone concurrently. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp); prednisone is a substrate of Pgp and it's active metabolite, prednisolone, is metabolized by CYP3A. Co-administration can increase prednisone exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Primidone: (Major) Coadministration of ivacaftor with primidone is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and primidone is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. Additionally, primidone is a CYP2C9 substrate and ivacaftor may inhibit CYP2C9. Coadministration may increase exposure to primidone leading to increased or prolonged therapeutic effects and adverse events. (Major) Do not administer tezacaftor; ivacaftor and primidone together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of primidone, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Quetiapine: (Moderate) Use caution when administering ivacaftor and quetiapine concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as quetiapine, can increase quetiapine exposure leading to increased or prolonged therapeutic effects and adverse events.
    Quinine: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with quinine; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); quinine is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If quinine and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and quinine is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Ramelteon: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as ramelteon. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; ramelteon is partially metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as ramelteon, can theoretically increase ramelteon exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Ribociclib: (Major) If ribociclib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ribociclib is a strong CYP3A4 inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ribociclib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, give 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ribociclib is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Ribociclib; Letrozole: (Major) If ribociclib and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ribociclib is a strong CYP3A4 inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ribociclib; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, give 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ribociclib is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Rifabutin: (Major) Administration of ivacaftor with strong CYP3A inducers, such as rifabutin, is not recommended because sub-therapeutic ivacaftor exposure could result. Ivacaftor is a CYP3A substrate. Co-administration with rifampin, another strong CYP3A inducer, decreased the ivacaftor exposure by approximately 9-fold. Ivacaftor is also an inhibitor of CYP3A, and rifabutin is metabolized by CYP3A. Co-administration may increase rifabutin exposure leading to increased or prolonged therapeutic effects and adverse events. (Major) Do not administer tezacaftor; ivacaftor and rifabutin together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of rifabutin, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Rifampin: (Major) Coadministration of ivacaftor with rifampin is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and rifampin is a strong CYP3A4 inducer. Coadministration with rifampin significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and rifampin together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of rifampin, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with rifampin decreased ivacaftor exposure 89%.
    Rifaximin: (Moderate) Although the clinical significance of this interaction is unknown, concurrent use of rifaximin, a P-glycoprotein (P-gp) substrate, and ivacaftor, a P-gp inhibitor, may substantially increase the systemic exposure to rifaximin; caution is advised if these drugs must be administered together. During one in vitro study, coadministration with cyclosporine, a potent P-gp inhibitor, resulted in an 83-fold and 124-fold increase in the mean Cmax and AUC of rifaximin, respectively. In patients with hepatic impairment, the effects of reduced metabolism and P-gp inhibition may further increase exposure to rifaximin. In addition, rifaximin was shown to induce CYP3A in in vitro models; however, absorption after oral administration is low and in patients with normal liver function, rifaximin is not expected to induce CYP3A4.
    Ritonavir: (Major) If ritonavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and ritonavir is a CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with ritonavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); ritonavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Rivaroxaban: (Minor) The coadministration of rivaroxaban and ivacaftor should be undertaken with caution in patients with renal impairment; it is unclear whether a clinically significant interaction occurs when these two drugs are coadministered to patients with normal renal function. Ivacaftor is a combined mild CYP3A4 inhibitor and mild P-glycoprotein (P-gp) inhibitor. Rivaroxaban is a substrate of CYP3A4/5 and the P-gp transporter. Coadministration in patients with renal impairment may result in increased exposure to rivaroxaban compared with patients with normal renal function and no inhibitor use since both pathways of elimination are affected. While an increase in exposure to rivaroxaban may be expected, results from an analysis of the ROCKET-AF trial which allowed concomitant administration of rivaroxaban and a combined P-gp inhibitor and weak or moderate CYP3A4 inhibitor did not show an increased risk of bleeding in patients with CrCl 30 to < 50 ml/min [HR (95% CI): 1.05 (0.77, 1.42)].
    Saquinavir: (Major) If saquinavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and saquinavir is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with saquinavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); saquinavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Sertraline: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sertraline. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; sertraline is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as sertraline, can theoretically increase sertraline exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Sildenafil: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; sildenafil is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as sildenafil, can theoretically increase sildenafil exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Simvastatin: (Minor) Use caution when administering ivacaftor and simvastatin concurrently. Coadministration of ivacaftor with simvastatin may increase simvastatin exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined. Simvastatin is a sensitive CYP3A4 substrate; ivacaftor is a weak CYP3A4 inhibitor.
    Simvastatin; Sitagliptin: (Minor) Use caution when administering ivacaftor and simvastatin concurrently. Coadministration of ivacaftor with simvastatin may increase simvastatin exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined. Simvastatin is a sensitive CYP3A4 substrate; ivacaftor is a weak CYP3A4 inhibitor.
    Sirolimus: (Moderate) Administration of tezacaftor; ivacaftor may increase the systemic exposure of sirolimus. Appropriate monitoring should be used; adjust sirolimus dosage as necessary. Sirolimus is a P-gp substrate; ivacaftor is a weak inhibitor of P-gp. (Moderate) Use caution when administering ivacaftor and sirolimus concurrently; careful monitoring of sirolimus blood concentrations is warranted. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as sirolimus, can increase sirolimus exposure leading to increased or prolonged therapeutic effects and adverse events.
    Sofosbuvir; Velpatasvir: (Moderate) Use caution when administering velpatasvir with ivacaftor. Taking these drugs together may increase the plasma concentrations of velpatasvir, potentially resulting in adverse events. Velpatasvir is a substrate of the drug transporter P-glycoprotein (P-gp); ivacaftor is a weak inhibitor of P-gp. Ivacaftor is also a weak inhibitor of the hepatic enzyme CYP3A4. Velpatasvir is a CYP3A4 substrate.
    Sofosbuvir; Velpatasvir; Voxilaprevir: (Moderate) Use caution when administering velpatasvir with ivacaftor. Taking these drugs together may increase the plasma concentrations of velpatasvir, potentially resulting in adverse events. Velpatasvir is a substrate of the drug transporter P-glycoprotein (P-gp); ivacaftor is a weak inhibitor of P-gp. Ivacaftor is also a weak inhibitor of the hepatic enzyme CYP3A4. Velpatasvir is a CYP3A4 substrate.
    St. John's Wort, Hypericum perforatum: (Major) Coadministration of ivacaftor with St. John's Wort is not recommended due to decreased plasma concentrations of ivacaftor. Ivacaftor is a sensitive CYP3A4 substrate and St. John's Wort is a strong CYP3A4 inducer. Coadministration with another strong CYP3A4 inducer significantly decreased ivacaftor exposure by approximately 9-fold. (Major) Do not administer tezacaftor; ivacaftor and St. John's Wort together; coadministration may reduce the efficacy of tezacaftor; ivacaftor. Exposure to ivacaftor is significantly decreased and exposure to tezacaftor may be reduced by the concomitant use of St. John's Wort, a strong CYP3A inducer; both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate). Coadministration of ivacaftor with a strong CYP3A inducer decreased ivacaftor exposure 89%.
    Sufentanil: (Moderate) Because the dose of the sufentanil sublingual tablets cannot be titrated, consider an alternate opiate if ivacaftor must be administered. Consider a reduced dose of sufentanil injection with frequent monitoring for respiratory depression and sedation if concurrent use of ivacaftor is necessary. If ivacaftor is discontinued, consider increasing the sufentanil injection dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Sufentanil is a CYP3A4 substrate, and coadministration with a weak CYP3A4 inhibitor like ivacaftor can increase sufentanil exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of sufentanil. If ivacaftor is discontinued, sufentanil plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to sufentanil.
    Sulfamethoxazole; Trimethoprim, SMX-TMP, Cotrimoxazole: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sulfamethoxazole; trimethoprim, SMX-TMP. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Tacrolimus: (Major) Use caution when administering ivacaftor and tacrolimus concurrently; careful tacrolimus blood concentrations is warranted. Ivacaftor is an inhibitor of CYP3A, and tacrolimus is a CYP3A substrate. Co-administration can increase tacrolimus exposure leading to increased or prolonged therapeutic effects and adverse events. (Moderate) Administration of tezacaftor; ivacaftor may increase the systemic exposure of tacrolimus. Appropriate monitoring should be used; adjust tacrolimus dosage as necessary. Tacrolimus is a P-gp substrate; ivacaftor is a weak inhibitor of P-gp.
    Talazoparib: (Moderate) Monitor for an increase in talazoparib-related adverse reactions if coadministration with ivacaftor is necessary. Talazoparib is a P-glycoprotein (P-gp) substrate and ivacaftor is a P-gp inhibitor. Coadministration with other P-gp inhibitors increased talazoparib exposure by 8% to 45%.
    Telithromycin: (Major) If telithromycin and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and telithromycin is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with telithromycin; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); telithromycin is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Temsirolimus: (Moderate) Monitor for an increase in temsirolimus-related adverse reactions if coadministration with ivacaftor is necessary. Temsirolimus is a P-glycoprotein (P-gp) substrate. Both ivacaftor and its M1 metabolite have the potential to inhibit P-gp. Concomitant use is likely to lead to increased concentrations of temsirolimus. (Moderate) Monitor for an increase in temsirolimus-related adverse reactions if coadministration with tezacaftor; ivacaftor is necessary. Temsirolimus is a P-glycoprotein (P-gp) substrate and tezacaftor is a P-gp inhibitor. Concomitant use is likely to lead to increased concentrations of temsirolimus.
    Tenofovir Alafenamide: (Minor) Use caution when administering ivacaftor and tenofovir alafenamide concurrently. Ivacaftor is an inhibitor of the drug transporter P-glycoprotein (P-gp). Tenofovir alafenamide is a substrate for P-gp. Concurrent use can increase tenofovir exposure leading to adverse events. Of note, when tenofovir alafenamide is administered as part of a cobicistat-containing product, its availability is increased by cobicistat and a further increase of tenofovir alafenamide concentrations is not expected upon coadministration of an additional P-gp inhibitor.
    Tenofovir, PMPA: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as ivacaftor. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Terbinafine: (Moderate) Due to the risk for terbinafine related adverse effects, caution is advised when coadministering ivacaftor. Although this interaction has not been studied by the manufacturer, and published literature suggests the potential for interactions to be low, taking these drugs together may increase the systemic exposure of terbinafine. Predictions about the interaction can be made based on the metabolic pathways of both drugs. Terbinafine is metabolized by at least 7 CYP isoenyzmes, with major contributions coming from CYP2C9 and CYP3A4; ivacaftor is an inhibitor of these enzymes. Monitor patients for adverse reactions if these drugs are coadministered.
    Ticagrelor: (Minor) Coadministration of ticagrelor and ivacaftor may result in increased exposure to ticagrelor which may increase the bleeding risk. Ticagrelor is a P-glycoprotein (P-gp) substrate and ivacaftor is a mild P-gp inhibitor. Based on drug information data with cyclosporine, no dose adjustment is recommended by the manufacturer of ticagrelor. Use combination with caution and monitor for evidence of bleeding.
    Tipranavir: (Major) If tipranavir and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and tipranavir is a CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with tipranavir; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); tipranavir is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Tolbutamide: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as tolbutamide. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Tolvaptan: (Moderate) Use caution when administering ivacaftor and tolvaptan concurrently. Ivacaftor is an inhibitor of CYP3A and P-glycoprotein (Pgp). Co-administration of ivacaftor with CYP3A and Pgp substrates, such as tolvaptan, can increase tolvaptan exposure leading to increased or prolonged therapeutic effects and adverse events.
    Topotecan: (Major) Avoid coadministration of ivacaftor with oral topotecan due to increased topotecan exposure; ivacaftor may be administered with intravenous topotecan. Oral topotecan is a substrate of P-glycoprotein (P-gp) and ivacaftor is a weak P-gp inhibitor. Oral administration within 4 hours of another P-gp inhibitor increased the dose-normalized AUC of topotecan lactone and total topotecan 2-fold to 3-fold compared to oral topotecan alone.
    Torsemide: (Minor) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as torsemide. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.
    Tramadol: (Minor) Use caution when administering ivacaftor and tramadol concurrently. Ivacaftor is an inhibitor of CYP3A and tramadol is partially metabolized by CYP3A. Co-administration can theoretically increase tramadol exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
    Trandolapril; Verapamil: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with verapamil; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); verapamil is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If verapamil and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and verapamil is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Triazolam: (Moderate) Monitor for serious adverse events, such as prolonged hypnotic and/or sedative effects during coadministration of ivacaftor and triazolam. Ivacaftor is a weak CYP3A inhibitor, and triazolam is a sensitive CYP3A substrate. Coadministration of ivacaftor with another sensitive CYP3A substrate increased exposure by 1.5-fold.
    Venetoclax: (Major) Reduce the dose of venetoclax by at least 50% and monitor for venetoclax toxicity (e.g., hematologic toxicity, GI toxicity, and tumor lysis syndrome) if coadministered with ivacaftor due to the potential for increased venetoclax exposure. Resume the original venetoclax dose 2 to 3 days after discontinuation of ivacaftor. Venetoclax is a CYP3A4 and P-glycoprotein (P-gp) substrate; ivacaftor is a CYP3A4 (weak) and P-gp inhibitor. Coadministration with a single dose of another P-gp inhibitor increased venetoclax exposure by 78% in a drug interaction study.
    Verapamil: (Major) Adjust the tezacaftor; ivacaftor dosing schedule when coadministered with verapamil; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet every other day in the morning and 1 ivacaftor tablet every other day in the morning on alternate days (i.e., tezacaftor/ivacaftor tablet on Day 1 and ivacaftor tablet on Day 2). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); verapamil is a moderate CYP3A inhibitor. Coadministration of a moderate CYP3A inhibitor increased ivacaftor exposure 3-fold. Simulation suggests a moderate inhibitor may increase tezacaftor exposure 2-fold. (Major) If verapamil and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to once daily. Ivacaftor is a CYP3A substrate and verapamil is a moderate CYP3A inhibitor. Coadministration with another moderate CYP3A inhibitor increased ivacaftor exposure by 3-fold.
    Voriconazole: (Major) If voriconazole and ivacaftor are taken together, administer ivacaftor at the usual recommended dose but reduce the frequency to twice weekly. Ivacaftor is a CYP3A substrate and voriconazole is a strong CYP3A inhibitor. Coadministration with another strong CYP3A inhibitor increased ivacaftor exposure by 8.5-fold. (Major) Reduce the dosing frequency of tezacaftor; ivacaftor when coadministered with voriconazole; coadministration may increase tezacaftor; ivacaftor exposure and adverse reactions. When combined, dose 1 tezacaftor; ivacaftor combination tablet twice a week, approximately 3 to 4 days apart (i.e., Day 1 and Day 4). The evening dose of ivacaftor should not be taken. Both tezacaftor and ivacaftor are CYP3A substrates (ivacaftor is a sensitive substrate); voriconazole is a strong CYP3A inhibitor. Coadministration of a strong CYP3A inhibitor increased tezacaftor and ivacaftor exposure 4- and 15.6-fold, respectively.
    Warfarin: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as warfarin. In vitro studies showed ivacaftor to be a weak inhibitor of CYP2C9. Co-administration may lead to increased exposure to CYP2C9 substrates; however, the clinical impact of this has not yet been determined.

    PREGNANCY AND LACTATION

    Pregnancy

    There are limited and incomplete human data from clinical trials and postmarketing reports on the use of tezacaftor; ivacaftor during human pregnancy to inform a drug-associated risk. Separate oral administration of tezacaftor and ivacaftor was not found to be teratogenic or result in adverse developmental effects in animals at doses approximately 0.2 to 3 times and 4 to 16 times the maximum recommended human dose (MRHD), respectively. No adequate and well-controlled studies have been performed in pregnant women.

    There is no information regarding the presence of tezacaftor or ivacaftor in human milk, the effects on the breast-feeding infant, or the effects on milk production. Both tezacaftor and ivacaftor are excreted into the breast milk of lactating rats; however, due to species-specific differences in lactation physiology, animal lactation data may not reliably predict levels in human milk. No studies have been done to assess the effects of tezacaftor; ivacaftor on a nursing infant. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    MECHANISM OF ACTION

    Tezacaftor; ivacaftor increases the quantity and function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride channel present at the surface of epithelial cells in multiple organs, resulting in increases in chloride transplant. Patients with cystic fibrosis (CF) have a mutation in the CFTR gene that encodes the protein. In patients with the F508del mutation, CFTR protein misfolding causes a defect in cellular processing and trafficking that targets the protein for degradation, resulting in a lower quantity of CFTR at the cell surface. The small amount of F508del-CFTR that does reach the cell surface is less stable and has low channel-open probability compared to the wild-type CFTR protein. Tezacaftor facilitates the cellular processing and trafficking of normal and select mutant forms of CFTR (including F508del-CFTR) to increase the amount of mature CFTR protein delivered to the cell surface. Ivacaftor is a CFTR potentiator that increases chloride transport by potentiating the channel-opening probability of the CFTR protein. CFTR protein must be present at the cell surface for ivacaftor to function. Ivacaftor can potentiate the CFTR protein delivered to the cell surface by tezacaftor, leading to a further enhancement of chloride transport than either agent alone.

    PHARMACOKINETICS

    Tezacaftor; ivacaftor is administered orally. Tezacaftor and ivacaftor are both approximately 99% protein bound, with tezacaftor binding primarily to albumin and ivacaftor binding primarily to albumin and alpha1-acid glycoprotein. The mean apparent Vd of tezacaftor and ivacaftor is 271 +/- 157 L and 206 +/- 82.9 L, respectively, in patients with cystic fibrosis (CF) in the fed state. Tezacaftor is extensively metabolized, primarily by CYP3A, to the 3 major metabolites M1 (pharmacologically active; similar potency to that of parent drug), M2 (much less pharmacologically active than parent drug or M1), and M5 (pharmacologically inactive). The majority of the drug (72%) is excreted in the feces unchanged. Ivacaftor is extensively metabolized, primarily by CYP3A, to the major metabolites M1 (pharmacologically active; one-sixth the potency of parent drug) and M6 (pharmacologically inactive). Ivacaftor is primarily eliminated in the feces (87.8%). Much smaller amounts of tezacaftor (14%) and ivacaftor (6.6%) are eliminated in the urine. Typical apparent clearance of tezacaftor is estimated to be 1.31 +/- 0.41 L/hour for patients with CF in the fed state; half-life is approximately 15 +/- 3.44 hours (CF patients). When given in combination with tezacaftor, the typical apparent clearance of ivacaftor is estimated to be 15.7 +/- 6.38 L/hour for CF patients in the fed state; half-life is approximately 13.7 +/- 6.06 hours (CF patients).
     
    Affected cytochrome P450 isoenzymes and drug transporters: CYP3A, CYP2C9, and P-gp
     
    Tezacaftor and ivacaftor are substrates of CYP3A (ivacaftor is a sensitive substrate of CYP3A). Tezacaftor; ivacaftor exposure is decreased when given with CYP3A inducers and increased when given with CYP3A inhibitors; exposures can be expected to decrease significantly during co-administration with strong CYP3A inducers. Ivacaftor is an inhibitor of P-gp and, based on in vitro studies, has the potential to inhibit CYP3A and CYP2C9. In vitro studies suggest tezacaftor has a low potential to inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. Tezacaftor has a low potential to induce CYP3A, but it is not an inducer of CYP1A2 and CYP2B6. Tezacaftor has a low potential to inhibit transporters P-gp, BCRP, OATP1B1, OATP1B3, OCT2, OAT1, or OAT3.