Misoprostol: A prostaglandin E1 analogue

Abstract

The pharmacology, pharmacokinetics, clinical efficacy, contraindications and precautions, adverse effects, dosage, and cost of misoprostol are reviewed. Misoprostol is a synthetic analogue of natural prostaglandin E1. It produces a dose-related inhibition of gastric acid and pepsin secretion and enhances mucosal resistance to injury. Misoprostol is extensively absorbed from the stomach and undergoes rapid de-esterification to its biologically active metabolite, misoprostol acid. The average absorption after an oral dose is 88%; peak plasma concentrations of misoprostol acid are achieved in less than 30 minutes. Clinical trials have demonstrated ulcer healing rates of approximately 60-80% in patients with duodenal ulcers who received misoprostol 800 micrograms daily for four weeks. Misoprostol was generally no more efficacious than conventional therapy with the H2-receptor antagonists cimetidine and ranitidine. The healing rate observed for gastric ulcers was less than that observed for duodenal ulcers. In trials involving healthy volunteers and patients with arthritis receiving aspirin, naproxen, tolmetin, ibuprofen, or piroxicam, misoprostol was consistently superior to placebo, cimetidine, and sucralfate in the prevention of nonsteroidal anti-inflammatory drug (NSAID)-induced gastropathy. The majority of these studies have been of short duration; however, long-term studies (up to three months) have corroborated superiority over placebo. Misoprostol is an abortifacient and is contraindicated in pregnant women and women of childbearing potential not using effective contraception. The most common adverse effect of misoprostol therapy is diarrhea, which is often mild and self-limiting and can be minimized by administration of misoprostol after meals and at bedtime. The cost (based on retail price) of four weeks of therapy with misoprostol is comparable to that of other antiulcer agents. Misoprostol has been shown to be an effective agent for the prevention of NSAID-induced gastric ulcers. However, there is no evidence that it offers any clinical advantage over H2-receptor antagonists for the treatment of gastric or duodenal ulcer disease.