CHEMET
Clinical safety rating
cautionComprehensive clinical and safety monograph for CHEMET (CHEMET).
Chelates heavy metals, particularly lead, mercury, and arsenic, by forming soluble complexes that are excreted renally. Acts as an antidote by binding to toxic metals and reducing their tissue concentrations.
| Metabolism | Metabolized in liver to disulfide dimers; undergoes enterohepatic circulation; primarily excreted renally as metabolites and unchanged drug. |
| Excretion | Renal: 80–90% as unchanged drug and metabolites (primarily as chelated complexes); biliary/fecal: <10%. |
| Half-life | Terminal elimination half-life: 1.6–3.5 hours (mean 2.1 h) in adults with normal renal function; prolonged in renal impairment (up to 20 h). |
| Protein binding | Approximately 80% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 0.5–0.8 L/kg, indicating distribution mainly in extracellular fluid; limited intracellular penetration. |
| Bioavailability | 20–40% after oral administration due to first-pass metabolism and limited absorption. |
| Onset of Action | Oral: chelation effect begins within 1–2 hours; maximal urinary metal excretion at 2–4 hours post-dose. IV: within minutes for chelation. |
| Duration of Action | 4–6 hours for single oral dose; chelation effect persists for 6–8 hours post-dose. Clinical effect (reduction of metal toxicity) requires repeated dosing over weeks. |
| Molecular Weight | 252.36 |
10-20 mg/kg orally every 8 hours for 5 days; maximum single dose 1250 mg.
| Dosage form | CAPSULE |
| Renal impairment | GFR 50-80 mL/min: same dose every 12 hours. GFR 10-49 mL/min: same dose every 24 hours. GFR <10 mL/min: same dose every 48 hours. |
| Liver impairment | No specific recommendations; caution in severe hepatic impairment (Child-Pugh C) due to potential toxicity. |
| Pediatric use | Children >1 year: 10-20 mg/kg/dose orally every 8 hours for 5 days; maximum 1250 mg/dose. |
| Geriatric use | Consider starting at lower end of dosing range (10 mg/kg) due to potential renal impairment; adjust per renal function. |
| 1st trimester | Animal studies show teratogenic effects; use only if benefit outweighs risk. |
| 2nd trimester | Limited human data; potential fetal harm; avoid unless clearly needed. |
| 3rd trimester | Risk of neonatal toxicity; avoid in late pregnancy unless essential. |
Clinical note
Comprehensive clinical and safety monograph for CHEMET (CHEMET).
| Placental transfer | Crosses placenta (animal studies); human data limited. |
| Breastfeeding | Excreted in breast milk; avoid breastfeeding due to potential infant toxicity (e.g., skin rash, renal effects). |
| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: No adequate studies, but animal studies show fetal resorption at maternally toxic doses, risk cannot be excluded. Second and third trimesters: No specific teratogenicity, but may cause anemia in fetus due to maternal chelation of essential metals. Avoid use unless clearly needed. |
| Fetal Monitoring | Monitor maternal CBC, liver function, renal function, and serum electrolytes weekly. Assess fetal growth by ultrasound if used in second/third trimester. Monitor for fetal distress if used near term. |
| Fertility Effects | No specific studies on fertility in humans. Animal studies show no impairment of fertility. However, due to potential zinc depletion, may theoretically affect spermatogenesis or ovulation; monitor if fertility is a concern. |
■ FDA Black Box Warning
None
| Serious Effects |
Known hypersensitivity to dimercaprol or any componentIron deficiency anemia (except in combined poisoning with other metals)Renal failure (unless dialysis available)
| Precautions | May cause nephrotoxicity; monitor renal function, May cause hypersensitivity reactions, including fever, rash, and anaphylaxis, Monitor for neutropenia; obtain CBC before and during therapy, Use caution in patients with hepatic impairment or glucose-6-phosphate dehydrogenase (G6PD) deficiency, May chelate essential minerals (e.g., zinc, copper); monitor levels with prolonged use, Not recommended for routine use in asymptomatic lead poisoning with low blood lead levels |
| Food/Dietary | No specific food interactions reported. However, due to gastrointestinal side effects (nausea, vomiting), it is advisable to maintain small, frequent meals. Avoid alcohol. |
| Clinical Pearls | Chelation therapy with dimercaprol (CHEMET) should be initiated within 4 hours of arsenic or mercury exposure for maximal efficacy. Administer only via deep intramuscular injection, never intravenously. Monitor renal function and urine output closely, as dimercaprol can cause nephrotoxicity. Alkalinize urine to pH 7.5-8.5 to decrease renal precipitation of metal-drug complexes. Use with caution in patients with glucose-6-phosphate dehydrogenase deficiency due to risk of hemolysis. Contraindicated in patients with peanut allergy (vehicle is peanut oil). |
| Patient Advice | This medication is given as a shot into a muscle, usually in the buttock. It may cause pain at the injection site. · You may experience a metallic taste, nausea, vomiting, headache, or burning sensation in the mouth or throat. · Drink plenty of fluids unless otherwise instructed to help flush metals from your body. · Avoid alcohol during treatment and for at least 48 hours after the last dose. · Report any signs of allergic reaction (rash, itching, difficulty breathing) or dark urine immediately. |
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