Adverse reactions to H2-receptor antagonists in Denmark before and after transfer of cimetidine and ranitidine to over-the-counter status.

The H2-receptor antagonists cimetidine and ranitidine were transferred from prescription only to over-the-counter (OTC) status in Denmark on March 27, 1989. Reports to the Danish Committee on Adverse Drug Reactions, a voluntary reporting system, have been evaluated to detect possible changes in frequency and pattern of adverse drug reactions (ADRs) caused by the altered delivery status. From the introduction of cimetidine in 1977 and until March 31, 1990, the Committee received 494 reports of 612 suspected adverse reactions to anti-ulcer drugs. The H2-receptor antagonists (mainly cimetidine and ranitidine) were responsible for 548 (90%) of the ADRs. The study, which presents experience with these drugs from more than a decade and a total consumption corresponding to 65 million treatment days, confirms their excellent safety record. Serious reactions were rare, and when they occurred, reversible. During the first year with cimetidine and ranitidine available OTC no changes were seen in reporting frequency or ADR pattern which could be ascribed to OTC transfer. Only one ADR report concerning OTC cimetidine was received. This may be caused by several factors: the safety of these drugs, the fact that only very little was actually sold OTC, and a relatively low sensitivity of the voluntary reporting system.