CLASSES
Antidotes, Systemic
Chelating Agents
DESCRIPTION
Oral lead chelating agent that forms water-soluble chelates that are excreted in the urine.
Used for the treatment of lead poisoning in pediatric patients with blood lead concentrations > 45 mg/dl.
Not a substitute for effective abatement of lead exposure.
COMMON BRAND NAMES
Chemet
HOW SUPPLIED
Chemet Oral Cap: 100mg
DOSAGE & INDICATIONS
For the treatment of lead toxicity secondary to serum lead concentrations > 45 mcg/dl.
NOTE: Succimer is not indicated for the prophylaxis of lead toxicity in a lead-containing environment. The use of succimer should always be accompanied by an identification and removal of the source of lead exposure. Identification of the lead source and its abatement are critical to a successful therapy outcome.
Oral dosage
NOTE: After succimer discontinuation, measure blood lead concentrations at least once weekly until stable. More frequent blood lead monitoring may be needed based on the initial blood lead concentration and the rate and degree of rebound of blood lead. Elevated blood lead concentrations and associated symptoms may return rapidly after succimer discontinuation because of redistribution of lead from bone stores to soft tissues and blood.
Adults†, Adolescents, and Children
Dosing is based on weight or BSA; approximately 10 mg/kg PO or 350 mg/m2 PO every 8 hours for the first 5 days. Subsequently, reduce frequency of dosing to every 12 hours and continue therapy for an additional 2 weeks. Each treatment course lasts a total of 19 days. As succimer is only available as 100 mg capsules, the weight-based dose must be adjusted to the available practical dose strength as follows:
-weight 8—15 kg: 100 mg/dose PO.
-weight 16—23 kg: 200 mg/dose PO.
-weight 24—34 kg: 300 mg/dose PO.
-weight 35—44 kg: 400 mg/dose PO.
-weight > 45 kg: 500 mg/dose PO.
The mg dose is given every 8 hours for days 1—5 and every 12 hours for days 6—19. Repeat courses may be necessary based upon the at least weekly blood lead concentration. At least 2 weeks between courses is advised unless the blood lead concentrations indicate the need for more prompt treatment. Uninterrupted dosing for longer than 3 weeks is not recommended, as the safety has not been established.
MAXIMUM DOSAGE
Adults
Safety and efficacy have not been established; used off label according to weight-based dosing. Maximum not to exceed 500 mg/dose PO.
Geriatric
Safety and efficacy have not been established.
Adolescents
> 45 kg: 500 mg/dose PO.
35—44 kg: 400 mg/dose PO.
24—34 kg: 300 mg/dose PO.
16—23 kg: 200 mg/dose PO.
8—15 kg: 100 mg/dose PO.
Children
> 45 kg: 500 mg/dose PO.
35—44 kg: 400 mg/dose PO.
24—34 kg: 300 mg/dose PO.
16—23 kg: 200 mg/dose PO.
8—15 kg: 100 mg/dose PO.
Infants
Safety and efficacy have not been established.
Neonates
Safety and efficacy have not been established.
DOSING CONSIDERATIONS
Hepatic Impairment
Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed. No data are available regarding the metabolism of succimer in patients with hepatic impairment. Closely monitor patients with a history of hepatic disease, as transient mild elevations in serum transaminases have occurred during treatment.
Renal Impairment
Specific guidelines for dosage adjustments in renal impairment are not available; it appears that no dosage adjustments are needed. Use with caution in patients with renal impairment.
Intermittent hemodialysis
Limited data suggest that succimer is dialyzable, but lead chelates are not.
ADMINISTRATION
Oral Administration
Oral Solid Formulations
Identifying the source of lead, and abatement and/or removal of the source, is a critical component of treatment.
Ensure adequate fluid intake prior to each dose and maintain good hydration during treatment.
In patients who cannot swallow, capsules may be opened and the beads sprinkled on a small amount of soft food or putting them on a spoon and following with a fruit drink.
STORAGE
Chemet:
- Avoid excessive heat (above 104 degrees F)
- Store between 59 to 77 degrees F
CONTRAINDICATIONS / PRECAUTIONS
General Information
Succimer is contraindicated for use in patients with a history of allergy to the drug.
Carefully observe patients during succimer receipt. After succimer discontinuation, elevated blood lead concentrations and associated symptoms may return rapidly because of lead redistribution from bone stores to soft tissues and blood. After succimer discontinuation, monitor blood lead concentrations at least once weekly until the concentration is stable. More frequent monitoring may be needed; consider the initial blood lead concentration and the rate and degree of rebound of blood lead.
Neutropenia
Mild to moderate neutropenia has been observed in some patients receiving succimer. There is limited experience with re-exposure to succimer in patients who have developed neutropenia during therapy. If a patient develops an absolute neutrophil count (ANC) below 1200/microliter, succimer should be withheld or discontinued. Re-exposure should be avoided unless the benefit of therapy clearly outweighs the potential risk of another episode of neutropenia and then only with careful patient monitoring. Patients should be counseled to promptly report any signs or symptoms of infection, which may indicate a lowered WBC count; if patients report infection, a CBC should be assessed.
Dehydration, dialysis, hypovolemia, renal failure, renal impairment
Use caution when administering succimer to a patient with renal impairment or renal failure, hypovolemia, or dehydration. Most of a succimer dose is excreted renally, including the water-soluble lead chelates. All patients undergoing treatment with succimer should remain adequately hydrated during therapy. Limited data suggests succimer is dialyzable, but the lead chelates are not; use caution in the patient on dialysis.
Hepatic disease
Patients with a history of hepatic disease should be monitored closely if treatment with succimer is indicated. Transient mild elevations in serum transaminases have occurred during treatment with succimer. Monitor serum transaminases before starting therapy with succimer and at least weekly during treatment. No data are available regarding the metabolism of succimer in patients with hepatic disease.
Pregnancy
Succimer should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant women; however, the drug has been found to be teratogenic and fetotoxic in pregnant mice.[15142] Exposure to lead can be a concern for maternal and fetal harm. Per CDC current guidelines, the essential actions for managing pregnant women with blood lead levels of 5 mcg/dL or more are removal of the lead source, disruption of the route of exposure, and avoidance of the lead-containing substance or activity. In circumstances where the maternal blood lead concentration is 45 mcg/dL or more, chelation therapy may be warranted after consultation with an expert in lead poisoning and perinatologists; for lower lead concentrations, data are insufficient to advise the use of chelation during pregnancy. Avoid chelation during the first trimester in all pregnant women, unless the lead intoxication is severe (maternal lead encephalopathy), due to the general concerns of drug use during organogenesis. Although no chelation-attributable toxicities have been reported in the existing published case reports of the treatment of pregnant women, very limited information is available to understand any potential short- or long-term effects for the fetus.[49776]
Breast-feeding
It is not known if succimer is excreted in human breast milk. Because many drugs and heavy metals are excreted in human milk, lactating mothers requiring succimer therapy should be discouraged from nursing infants.[15142] According to CDC guidelines, the risk of adverse developmental effects in infants with blood lead concentrations of 5 mcg/dL or more is of greater concern than the risks associated with not breast-feeding. Thus, the CDC encourages mothers with blood lead concentrations of 40 mcg/dL or more to pump and discard their breast milk until their blood lead levels drop below 40 mcg/dL. These recommendations are made for the US population and may not be appropriate for other countries, where infant mortality from other causes is a greater concern.[49776]
Infants, neonates
Safety and efficacy of succimer in infants and neonates have not been established. Use of chelation agents may be considered in some cases, but an expert in management of lead toxicity should be consulted.
ADVERSE REACTIONS
Severe
proteinuria / Delayed / 0-3.7
angioedema / Rapid / 0-1.0
arrhythmia exacerbation / Early / 0-1.0
Moderate
flank pain / Delayed / 5.2-15.7
hypercholesterolemia / Delayed / 4.2-10.4
elevated hepatic enzymes / Delayed / 4.2-10.4
hemorrhoids / Delayed / 1.0-10.0
peripheral neuropathy / Delayed / 1.0-10.0
oral ulceration / Delayed / 1.0-10.0
dysuria / Early / 0-3.7
urinary retention / Early / 0-3.7
neutropenia / Delayed / 0-1.0
thrombocytosis / Delayed / 0-1.0
eosinophilia / Delayed / 0-1.0
Mild
back pain / Delayed / 5.2-15.7
fever / Early / 5.2-15.7
abdominal pain / Early / 5.2-15.7
chills / Rapid / 5.2-15.7
headache / Early / 5.2-15.7
fatigue / Early / 5.2-15.7
pruritus / Rapid / 2.6-11.2
anorexia / Delayed / 1.0-10.0
dizziness / Early / 1.0-10.0
paresthesias / Delayed / 1.0-10.0
irritability / Delayed / 1.0-10.0
maculopapular rash / Early / 1.0-10.0
vesicular rash / Delayed / 1.0-10.0
rash / Early / 4.0-4.0
cough / Delayed / 0.7-3.7
nasal congestion / Early / 0.7-3.7
throat irritation / Early / 0.7-3.7
rhinorrhea / Early / 0.7-3.7
lacrimation / Early / 1.0-3.7
infection / Delayed / 0-1.0
urticaria / Rapid / 0-1.0
diarrhea / Early / 10.0
metallic taste / Early / 10.0
nausea / Early / 10.0
vomiting / Early / 10.0
drowsiness / Early / 10.0
DRUG INTERACTIONS
Dimercaprol: (Moderate) Concomitant use of succimer and other chelation therapy such as edetate calcium disodium, calcium EDTA (CaNa2EDTA) with or without dimercaprol (BAL) is not recommended, as data are not available. Patients who have received CaNa2EDTA with or without dimercaprol may use succimer for subsequent treatment after an interval of 4 weeks.
Edetate Calcium Disodium, Calcium EDTA: (Moderate) Concomitant use of succimer and other chelation therapy such as edetate calcium disodium, calcium EDTA (CaNa2EDTA) with or without dimercaprol (BAL) is not recommended, as data are not available. Patients who have received CaNa2EDTA with or without dimercaprol may use succimer for subsequent treatment after an interval of 4 weeks.
Edetate Disodium, Disodium EDTA: (Moderate) Concomitant use of succimer and other chelation therapy such as edetate calcium disodium, calcium EDTA (CaNa2EDTA) with or without dimercaprol (BAL) is not recommended, as data are not available. Patients who have received CaNa2EDTA with or without dimercaprol may use succimer for subsequent treatment after an interval of 4 weeks.
PREGNANCY AND LACTATION
Pregnancy
Succimer should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant women; however, the drug has been found to be teratogenic and fetotoxic in pregnant mice.[15142] Exposure to lead can be a concern for maternal and fetal harm. Per CDC current guidelines, the essential actions for managing pregnant women with blood lead levels of 5 mcg/dL or more are removal of the lead source, disruption of the route of exposure, and avoidance of the lead-containing substance or activity. In circumstances where the maternal blood lead concentration is 45 mcg/dL or more, chelation therapy may be warranted after consultation with an expert in lead poisoning and perinatologists; for lower lead concentrations, data are insufficient to advise the use of chelation during pregnancy. Avoid chelation during the first trimester in all pregnant women, unless the lead intoxication is severe (maternal lead encephalopathy), due to the general concerns of drug use during organogenesis. Although no chelation-attributable toxicities have been reported in the existing published case reports of the treatment of pregnant women, very limited information is available to understand any potential short- or long-term effects for the fetus.[49776]
It is not known if succimer is excreted in human breast milk. Because many drugs and heavy metals are excreted in human milk, lactating mothers requiring succimer therapy should be discouraged from nursing infants.[15142] According to CDC guidelines, the risk of adverse developmental effects in infants with blood lead concentrations of 5 mcg/dL or more is of greater concern than the risks associated with not breast-feeding. Thus, the CDC encourages mothers with blood lead concentrations of 40 mcg/dL or more to pump and discard their breast milk until their blood lead levels drop below 40 mcg/dL. These recommendations are made for the US population and may not be appropriate for other countries, where infant mortality from other causes is a greater concern.[49776]
MECHANISM OF ACTION
Succimer is a lead chelator. It forms water soluble chelates, which increases the urinary excretion of lead.
PHARMACOKINETICS
Succimer is administered orally. After 10 mg/kg of succimer was administered orally to healthy adults, succimer was rapidly and extensively metabolized. Approximately 25% of the dose was excreted in the urine, with peak blood concentration and urinary excretion occurring between 2 and 4 hours. Only 10% of succimer excreted in the urine was excreted as unchanged drug. The majority of drug excreted in the urine occurred as mixed succimer-cysteine disulfides.
Succimer lowers blood lead concentrations. For example, among adults with blood lead concentrations of 44—96 mcg/dl who received oral succimer, the mean lead blood concentrations decreased 72.5% after 5 days of 10 mg/kg orally every 8 hours, 58.3% after 5 days of 6.7 mg/kg every 8 hours, and 35.5% after 5 days of 3.3 mg/kg every 8 hours. In the initial 24 hours after receipt of the 10 mg/kg dose, the mean urinary excretion of lead was 28.6 times the pretreatment 24 hour urinary lead excretion. As the chelatable pool was reduced during treatment, urinary lead output decreased. In addition to adults, succimer also lowers blood lead concentrations in children. Among children 2—7 years of age who received 350 mg/m2 every 8 hours for 5 days, the mean blood lead concentration decreased 78%. Unfortunately, both adults and pediatric patients experienced a rebound in blood lead concentrations after succimer discontinuation. For example, after receipt of 350 mg/m2 (10 mg/kg) every 8 hours for 5 days, the mean lead concentration rebounded and plateaued at 60—85% of pretreatment concentrations 2 weeks after therapy.
Succimer receipt beyond 5 days was studied to examine the effect of longer dosing on the rebound of blood lead concentrations. Children 1—7 years of age with blood lead concentrations of 42—67 mcg/dl who received 350 mg/m2 every 12 hours for 2 weeks after the initial 5 days of 350 mg/m2 every 8 hours did not experience rebound of blood lead concentrations after the initial 5-day treatment period. Further, less rebound was noted after succimer discontinuation. In another study, 10 children aged 21—72 months with blood lead concentrations of 30—57 mcg/dl received succimer 350 mg/m2 by mouth every 8 hours for 5 days, followed by 350 mg/m2 by mouth every 12 hours for an additional 19 to 22 days. Blood lead concentrations decreased and remained stable under 15 mcg/dl during the extended dosing period. Succimer is indicated for a total therapy duration of 19 days, and additional treatment courses may be needed.
Succimer had no significant effect on the excretion of iron, calcium, or magnesium; zinc excretion doubled.
Oral Route
In a study of healthy volunteers, after the administration of a single dose of radiolabeled succimer, absorption was rapid but variable with peak blood radioactivity concentrations occurring within 1 to 2 hours after administration.