Enprostil, a synthetic analogue of prostaglandin E2, is effective in the treatment of patients with duodenal or gastric ulcers. As demonstrated in pharmacological studies in healthy volunteers and in patients with inactive ulcer disease, gastric acid secretion is suppressed by up to 80% for almost 12 hours after single doses of enprostil. The drug also reduces the secretion of pepsin, another 'aggressive' factor in peptic ulcer disease. Interestingly, in contrast to the H2-receptor antagonists, which either increase or have no effect on serum gastrin concentrations, enprostil inhibits basal and postprandial gastrin release. Although the possible effects of enprostil on 'defensive' factors in peptic ulcer disease-which are thought to protect the mucosa-require much further clarification, some evidence obtained in man indicates that bicarbonate secretion is enhanced by enprostil. Further, data from animal studies suggest that microvascular integrity may be preserved by a direct action of enprostil on the gastric mucosa. In healthy volunteers, the administration of enprostil in antisecretory doses protects the gastric mucosa against of enprostil in antisecretory doses protects the gastric mucosa against aspirin-induced injury. Cumulative rates of ulcer healing observed in patients with duodenal ulcers after 4 weeks' treatment with enprostil 35 micrograms twice daily were about 50 to 80%, which were similar to those seen in comparative trials with usual therapeutic doses of cimetidine or pirenzepine, but less than occurred with ranitidine. Moreover, enprostil has been shown to relieve daytime pain in a similar percentage of patients as do these H2-receptor antagonists, but night-time pain appears to respond less well to therapy with the prostaglandin. As evidenced by a few controlled trials in patients with gastric ulcers, treatment with enprostil 35 micrograms twice daily for 6 weeks provides ulcer healing in parallel with pain relief as effectively as cimetidine and ranitidine in a high percentage of patients (about 80% after 6 weeks). Prophylactic treatment with enprostil after initial ulcer healing has reduced the rate of duodenal ulcer relapse in patients 'at risk', but to a lesser extent than has ranitidine. Gastrointestinal symptoms-abdominal cramping and pain, flatulence, nausea and notably, diarrhoea-are the most frequently reported side effects during therapy with enprostil. Diarrhoea occurs in about 10% of patients, but is rarely of a severity necessitating treatment discontinuation.(ABSTRACT TRUNCATED AT 400 WORDS)