Cimetidine-associated optic neuropathy.

Two cases of optic neuropathy associated with cimetidine therapy are reported. Recovery occurred in both after drug withdrawal. Rechallenge with the same agent totally reproduced the condition in the first case. Cimetidine exerts an unequivocal toxicity on the central and peripheral nervous systems. Since its introduction in 1976, it has been used in over 100 million patients, but only 3 cases of optic neuropathy have been reported as far as we know. Although the mechanism of toxicity is still unclear, cimetidine is a well-recognized zinc chelator, and zinc deficiency has been implicated in causing optic neuropathy. Hence, it can be concluded that cimetidine produced this toxicity through its mechanism of zinc chelation. However, close ophthalmic follow-up of such patients is unnecessary, but an unexplained visual deterioration should prompt immediate drug withdrawal.