SIDE EFFECTS WITH OMEPRAZOLE?

Astra Pharmaceuticals' proton pump inhibitor Losec (omeprazole) has been associated with a number of reports of endocrine side effects, according to a study published in the British Medical Journal (August 22).

The study, carried out by the World Health Organization's Collaborating Centre for International Drug Monitoring, has identified 15 cases of impotence and 15 of breast enlargement (gynecomastia) which may be associated with omeprazole use. All the occurrences, which originated from eight countries, had been reported to the WHO's program for international drug monitoring as record cases, and in each case "causality seemed possible," according to the authors of the report.

Similar side effects have been reported with two other anti-ulcerants, SmithKline Beecham's Tagamet (cimetidine) and Glaxo's Zantac (ranitidine), although only cimetidine has shown any binding activity to androgen receptors. Looking at the pharmacology of omeprazole, there is no obvious identifiable mechanism to explain the observations. However, the fact that seven of the patients with impotence and five of those with gynecomastia recovered on cessation of the drug is strong evidence that omeprazole is the causative agent, note the authors.