T he histamine H2-neceptor antagonist cimetidine is an effective drug widely prescribed for the treatment of peptic ulcer disease (1). It is also useful in the treatment of gastric ulcers and erosive gastnitis and in the treatment and prevention of stress ulcers (1). It was initially thought that cimetidine had few adverse effects. With increased use cimetidine has been found (1-3) to cause mental confusion, bone marrow depression, and decreased sperm count and to interfere with the metabolism of drugs metabolized by cytochnome P448 and P450. Drugs that are metabolized by these mixed-function oxidase systems with metabolism inhibited by cimetidine are antipynine, warfanin, diazepam, chlordiazepoxide, propranolol, labetalol, theophylline, carbamazepine, and phenytoin (2). These interactions have been shown to have important, sometimes life-threatening, implications. We present a case of cimetidine interfering with imipnamine and desipramine metabolism, resulting in elevated serum concentrations of imipramine and desipnamine and in adverse effects in a patient receiving a usual therapeutic dose of irnipramine.
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Miller et al. (1983) studied this question.