Effects of prolonged oral cimetidine, ranitidine, and famotidine therapy on antipyrine elimination.

The effects of three histamine H2-receptor antagonists on the antipyrine metabolizing capacity of the liver were studied in 32 patients with gastrointestinal disorders and in three healthy volunteers. The drugs studied were 800 mg and 400 mg of cimetidine, 300 mg of ranitidine, and 40 mg of famotidine daily. Only cimetidine at 800 mg/day inhibited hepatic antipyrine metabolism, and the inhibitory effects disappeared rapidly with no accumulation.