Dimercaptosuccinic acid

Dimercaptosuccinic acid (DMSA), also called succimer, is a medication used to treat lead, mercury, and arsenic poisoning. When radiolabeled with technetium-99m, it is used in a number of types of diagnostic testing. A full course is 19 days of medications by mouth. More than two weeks should pass before a second course is given. Dimercaptosuccinic acid (DMSA), also called succimer, is a medication used to treat lead, mercury, and arsenic poisoning. When radiolabeled with technetium-99m, it is used in a number of types of diagnostic testing. A full course is 19 days of medications by mouth. More than two weeks should pass before a second course is given. Common side effects include vomiting, diarrhea, rash, and low blood neutrophil levels. Liver problems and allergic reactions may also occur with use. Whether use during pregnancy is safe for the baby is unclear. Dimercaptosuccinic acid is in the chelating agent family of medications. It works by binding with lead and a number of other heavy metals, allowing them to leave the body in the urine. Dimercaptosuccinic acid has been used medically since the 1950s. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. In the United States, no generic version was available as of 2015. A course of treatment costs more than US$200 (about $6.63 per 100-mg pill). In India, it costs about $1.24 per 100-mg pill. Dimercaptosuccinic acid is indicated for the treatment of lead poisoning in children with blood level measured above 45 µg/dl. The use of DMSA is not approved for prevention of lead poisoning in anticipation of exposure in known lead-contaminated environments. Its elimination half-life is 2.5–3.5 hours. DMSA can cross the blood–brain barrier of mice, but not that of humans, limiting its use to extracting heavy metals from parts of the body other than the central nervous system. DMSA facilitates urinary excretion of lead, and with sufficiently aggressive treatment, can reduce lead content in the brain. It also increases urinary excretion of copper and zinc. DMSA improved cognitive function in rats that had been exposed to lead, but reduced cognitive function in rats that had not been exposed to lead. The relative activities of a series of novel monoalkyl esters of meso-2,3-dimercaptosuccinic acid (MiADMSA) have been examined as agents for the mobilization of cadmium, lead and arsenic owing to the ability of these monoesters to cross cell membranes. The monoesters were found to be more effective than the parent compound DMSA. The complexes (monoesters of DMSA) seem to penetrate cells (not possible in the case of DMSA), which helps in targeting intracellular sites in the body and aids in the removal of toxic metal ions in the cytosol and organelles inside the cell. It is the organosulfur compound with the formula HO2CCH(SH)CH(SH)CO2H. This colorless solid contains two carboxylic acid and two thiol groups, the latter being responsible for its mildly unpleasant odour. It occurs in two diastereomers, meso and the chiral dl forms. The 2,3-dimercaptosuccinic acid molecule has two stereocentres (two asymmetric carbons), and can exist as three different stereoisomers. The 2S,3S and 2R,3R isomers are a pair of enantiomers, whereas the 2R,3S isomer is a meso compound and thus optically inactive. DMSA may be prepared by reacting acetylenedicarboxylic acid with sodium thiosulfate or thioacetic acid followed by hydrolysis. The dimethyl ester is also known.