Drug-induced lichen planus.

Lichen planus is a relatively common skin disorder of unknown etiology. A wide variety of drugs have been implicated in its cause. Using five or more cases of drug-induced lichen planus reported in at least three separate reports with at least one case of probable cause by the scale of Naranjo et al as criteria, sufficient evidence exists that beta-blockers, methyldopa, penicillamine, quinidine, and quinine play a role in this disorder. Evidence is insufficient for angiotensin-converting enzyme inhibitors, sulfonylurea agents, carbamazepine, gold, lithium, and a host of miscellaneous drugs. Given available epidemiologic evidence, nonsteroidal antiinflammatory agents probably should also be considered causative. Differentiating drug-induced lichen planus from the idiopathic disorder is difficult; most evidence is based on the dechallenge and rechallenge with the drug when these data are available.