Chemical formula: C₄H₆O₄S₂ Molecular mass: 182.21 g/mol PubChem compound: 2724354
Succimer has been shown to be teratogenic and fetotoxic in pregnant mice when given subcutaneously in a dose range of 410 to 1640 mg/kg/day during the period of organogenesis. In a developmental study in rats, succimer produced maternal toxicity and deaths at the dose of 720 mg/kg/day or more during organogenesis.
The dose of 510 mg/kg/day was the highest tolerable dose in pregnant rats. Impaired development of reflexes was noted in pups of 720 mg/kg/day group dam. There are no adequate and well controlled studies in pregnant women. Succimer should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
It is not known whether this drug is excreted in human milk. Because many drugs and heavy metals are excreted in human milk, nursing mothers requiring succimer therapy should be discouraged from nursing their infants.
Succimer has not been tested for carcinogenic potential in long-term animal studies. Succimer up to a dose of 510 mg/kg/day in males and 100 mg/kg/day in females did not show any adverse effect on fertility and reproductive performance. It was not mutagenic in the Ames bacterial assay and in the mammalian cell forward gene mutation assay.
Clinical experience with succimer has been limited. Consequently, the full spectrum and incidence of adverse reactions including the possibility of hypersensitivity or idiosyncratic reactions have not been determined. The most common events attributable to succimer, i.e., gastrointestinal symptoms or increases in serum transaminases, have been observed in about 10% of patients. Rashes, some necessitating discontinuation of therapy, have been reported in about 4% of patients. If rash occurs, other causes (e.g. measles) should be considered before ascribing the reaction to succimer. Rechallenge with succimer may be considered if lead levels are high enough to warrant retreatment. Allergic reactions including urticaria and angioedema have been reported on repeated administration of the drug. Mild to moderate neutropenia has been observed in some patients receiving succimer. Table I presents adverse events reported with the administration of succimer for the treatment of lead and other heavy metal intoxication.
Table I. Incidence of adverse events in domestic studies regardless of attribution or succimer dosage:
| Pediatric Patients (191) | Adults (134) | |||
|---|---|---|---|---|
| % | (n) | % | (n) | |
| Digestive: | 12.0 | 23 | 20.9 | 28 |
| Nausea, vomiting, diarrhea, appetite loss, hemorrhoidal symptoms, loose stools, metallic taste in mouth. | ||||
| Body as a Whole: | 5.2 | 10 | 15.7 | 21 |
| Back pain, abdominal cramps, stomach pains, head pain, rib pain, chills, flank pain, fever, flulike symptoms, heavy head/tired, head cold, headache, moniliasis. | ||||
| Metabolic: | 4.2 | 8 | 10.4 | 14 |
| Elevated SGPT, SGOT, alkaline phosphatase, elevated serum cholesterol. | ||||
| Nervous: | 1.0 | 2 | 12.7 | 17 |
| Drowsiness, dizziness, sensorimotor neuropathy, sleepiness, paresthesia. | ||||
| 2.6 | 5 | 11.2 | 15 | |
| Papular rash, herpetic rash, rash, mucocutaneous eruptions, pruritus. | ||||
| Special Senses: | 1.0 | 2 | 3.7 | 5 |
| Cloudy film in eye, ears plugged, otitis media, eyes watery. | ||||
| Respiratory: | 3.7 | 7 | 0.7 | 1 |
| Throat sore, rhinorrhea, nasal congestion, cough. | ||||
| Urogenital: | 0.0 | - | 3.7 | 5 |
| Decreased urination, voiding difficulty, proteinuria increased. | ||||
| Cardiovascular: | 0.0 | - | 1.8 | 2 |
| Arrhythmia | ||||
| Heme/Lymphatic: | 0.5* | 1 | 1.5* 2 | |
| Mild to moderate neutropenia, increased platelet count, intermittent eosinophilia. | ||||
| Musculoskeletal: | 0.0 | - | 3.0 | 4 |
| Kneecap pain, leg pains. | ||||
* Does not include neutropenia
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