Ranitidine or cimetidine.

Ranitidine, a new H2-receptor blocking antihistamine, is pharmacokinetically similar to cimetidine, but its potency is about eightfold greater. The clinical response to ranitidine is more prolonged, largely because of potency and not kinetic advantage. Increased potency has not meant greater clinical efficacy: duodenal ulcer healing, at 4, 6, or 8 weeks of therapy, does not differ between ranitidine and the cheaper cimetidine. Compliance and overall safety appear excellent for both drugs at this time. The safety record and side effects of cimetidine, but not ranitidine, are well established. So far, side effects of ranitidine are minimal, and in some cases anecdotal, but they cannot be ignored. Emerging information suggests that, although the incidence and severity of certain side effects may prove different for ranitidine than cimetidine, the pattern of side effects is similar with both drugs.