Comparative effect of cimetidine and ranitidine on prolactin secretion.

Cimetidine has been shown to stimulate prolactin secretion after a intravenous administration. Cimetidine 200 mg and ranitidine 50 mg was given i.v. in a randomly allocated order to 22 volunteers on consecutive days; these doses can be regarded as equivalent as far as inhibition of gastric acid output is concerned. Plasma prolactin was estimated at regular intervals. The prolactin stimulating effect of cimetidine was confirmed while ranitidine did not influence plasma prolactin levels. Although cimetidine and ranitidine seem to be equally effective in reducing gastric acid output, the effect of the drugs are not the same on their entire spectrum of action since ranitidine does not influence plasma prolactin. It still has to be established in clinical trials which drug is the best choice in clinical medicine.