Our review of published material, manufacturer's files, and submissions to the United States Food and Drug Administration indicates that cimetidine is safe for short term use (up to 8 weeks). This judgment is based on a total experience with over 3000 patients. Clinically insignificant elevations of serum creatinine occur in a high percentage of patients, persisting until the end of therapy, then disappearing. Gynecomastia occurred in some patients on long term therapy.