Succimer

Succimer is a dimercaprol analog (meso-2,3-dimercaptosuccinic acid, DMSA) that chelates divalent heavy metals, primarily lead, through its sulfhydryl groups. It forms a water-soluble complex that is renally excreted, making it useful in patients with normal renal function. Unlike dimercaprol (BAL), succimer is administered orally, has fewer side effects, and does not require combination with EDTA. It is the preferred first-line chelator for symptomatic lead poisoning or significantly elevated blood lead levels (typically 45-69 mcg/dL) in children without encephalopathy, often used in outpatient settings. For severe lead poisoning with encephalopathy or very high levels (>70 mcg/dL), IV EDTA and dimercaprol are used instead, sometimes in combination with succimer. Succimer is also used for mercury and arsenic poisoning. Adverse effects include GI upset (nausea, vomiting, diarrhea), elevated liver enzymes, and neutropenia. It should be used cautiously in patients with renal impairment. Monitoring includes serial blood lead levels and LFTs during therapy. Unlike EDTA, succimer does not cause significant chelation of essential metals like zinc and calcium, making it a safer oral option for long-term management of chronic lead exposure.