The d-isomer of penicillamine, d-^b-dimethylcysteine, is used clinically, although the l-isomer also forms chelation complexes. Penicillamine is an effective chelator of copper, mercury, zinc, and lead and promotes the excretion of these metals in the urine.
ABSORPTION, DISTRIBUTION, AND EXCRETION
Penicillamine is well absorbed (40—70%) from the GI tract and therefore has a decided advantage over many other chelating agents. Food, antacids, and iron reduce its absorption. Peak concentrations in blood are obtained 1-3 hours after administration. Unlike cysteine, its nonmethylated parent compound, penicillamine, is somewhat resistant to attack by cysteine desulfhydrase or L-amino acid oxidase and is relatively stable in vivo. Hepatic biotransformation is responsible for most of the degradation of penicillamine, and very little is excreted unchanged. Metabolites are found in both urine and feces.
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