Inhibition of food stimulated acid secretion by misoprostol, an orally active synthetic E1 analogue prostaglandin

Helicobacter pylori infection, ABO blood group, and effect of misoprostol on gastroduodenal mucosa in NSAID-treated patients with rheumatoid arthritis

Our aim was to investigate the effect of misoprostol on NSAID-induced gastroduodenal mucosal damage in patients with rheumatoid arthritis. The study included 40 patients, and it was designed as a double-blind, placebo-controlled trial. Misoprostol significantly reduced the gastroduodenal mucosal lesions found at endoscopy (P < 0.05) and prevented the development of ulcers. The cumulative incidence of ulcers at four weeks was 5% in the placebo group and 0% in the misoprostol group. The basal and pentagastrin-stimulated acid output as evaluated after 23 days of treatment with misoprostol was not significantly affected. Forty-one percent of the patients had signs of current Helicobacter pylori infection, 33% had positive serology only, and 26% had no evidence of infection. Most of the patients with current infection belonged to blood group O (P < 0.05). Misoprostol treatment did not affect the occurrence of Helicobacter pylori or the rheumatic disease activity. It is concluded that the protective actions of misoprostol on the gastroduodenal mucosa of NSAID-treated patients are largely mediated by mechanisms other than inhibition of acid secretion. The relationship among active Helicobacter pylori infection, blood group O, and peptic ulcer may be helpful to identify a subpopulation of patients taking NSAIDs at risk of developing peptic ulcers.

Prostaglandins and gastric ulcers: from seminal vesicle to misoprostol (Cytotec)

Misoprostol (Cytotec, G.D. Searle & Company, Chicago, IL) is the first of a new class of orally administered prostaglandin analog drugs to be marketed in the United States. Misoprostol was approved for the prevention of gastric mucosal ulcers associated with nonsteroidal anti-inflammatory drugs (NSAIDS) in high-risk patients. This represents a potentially important development in the pharmacotherapy of peptic ulcer disease. The purposes of this article are to review (1) the biochemistry, physiology, and pharmacology of prostaglandins, especially those synthesized by the stomach; (2) the potential role of prostaglandin deficiency in the pathophysiology of gastric ulcer disease; and (3) the role of prostaglandin analogs in the prevention and therapy of gastric ulcer disease and in other conditions. As the mechanism of action of these new drugs differs from that of the histamine H2-receptor antagonists (H2-blockers), prostaglandin analogs will, whenever possible, be compared with the H2-blockers [cimetidine (Tagamet), ranitidine (Zantac), nizatidine (Axid) and famotidine (Pepcid)], currently the cornerstone of peptic ulcer therapy in this country.

A review of mucosal protection by synthetic prostaglandin E analogs against injury by non-steroidal anti-inflammatory agents

Non-steroidal anti-inflammatory agents (NSAIDs) damage the gastric mucosa both in normal volunteers and in arthritic patients. Four large studies have been done in our laboratory comparing the prostaglandin E analog misoprostol against placebo, cimetidine, and sucralfate. These studies showed that misoprostol protected the stomach significantly better than cimetidine or sucralfate. In the duodenum, misoprostol and cimetidine were equally effective. Comparison of secretory and anti-secretory doses of misoprostol reveal duodenal protection with the former but not with the latter, but gastric protection with both doses, suggesting that cytoprotective mechanisms other than acid suppression exist in the stomach in subjects taking prostaglandins. Adequately controlled and blind studies reported in the literature in arthritic patients are also reviewed, and it would appear that prostaglandins offer the best currently available method of providing mucosal protection for patients taking NSAIDs.

Antisecretory and mucosal protective actions of misoprostol. Potential role in the treatment of peptic ulcer disease

Misoprostol, a synthetic methyl ester analogue of prostaglandin E1, inhibits basal, nocturnal, and stimulated gastric acid secretion. In doses of 400 to 1,200 micrograms daily, misoprostol accelerates the healing of duodenal and gastric ulcers in humans. In addition to its antisecretory actions, misoprostol has gastroduodenal mucosal protective (cytoprotective) effects in animals and in humans. In humans, these cytoprotective actions have been demonstrated in acid-dependent studies using non-antisecretory doses and in acid-independent studies using antisecretory doses. Patients with peptic ulcer disease may have a relative deficiency of mucosal prostaglandin synthesis as compared with nonulcer control subjects. In addition, patients who consume nonsteroidal anti-inflammatory drugs and those who are cigarette smokers may also have depressed gastric mucosal prostaglandin synthesis. There is some evidence that misoprostol reverses the deleterious effect of smoking on duodenal ulcer healing and that it is effective in treating and preventing mucosal damage induced by nonsteroidal anti-inflammatory drugs and alcohol.

Misoprostol. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in the treatment of peptic ulcer disease

Misoprostol is an analogue of prostaglandin E1 and is the first synthetic prostaglandin analogue to be made available for the treatment of peptic ulcer disease. It inhibits gastric acid secretion in man, and there is also some evidence that it limits the extent of gastrointestinal damage induced by ulcerogenic agents in animals and healthy volunteers at doses lower than those required to inhibit acid secretion. This 'cytoprotective' activity has been explained by several mechanisms, but its contribution to the clinical efficacy of misoprostol in healing established ulcers is doubtful since the drug does not appear to be effective in healing peptic ulcers at non-antisecretory dosages. In clinical trials, ulcer healing has been reported in 60 to 85% of patients with duodenal ulcers and 32 to 54% with gastric ulcers receiving misoprostol 200 micrograms 4 times daily for 4 weeks--the recommended dosage. In comparative studies, the percentage of patients with healed ulcers after misoprostol (800 micrograms daily) was not significantly different from that with cimetidine (1200 mg daily), although there was greater pain relief with cimetidine. No study has yet been published concerning the use of misoprostol as maintenance therapy for the prevention of ulcer recurrence, and no long term tolerability data are available. However, in acute ulcer healing studies (2 to 12 weeks in duration) misoprostol has been well tolerated. Diarrhoea was the most commonly reported symptom, and this was only rarely of sufficient severity to interfere with treatment. No evidence of histopathological changes in the gastric mucosa induced by misoprostol have been reported in man. Evidence of uterine stimulant effects in women receiving misoprostol during the first trimester of pregnancy has resulted in the drug being contraindicated during pregnancy. Thus, misoprostol is a new type of antiulcer drug, providing an alternative approach to the therapy of peptic ulcer disease. It has been shown to be effective and well tolerated in the healing of both gastric and duodenal ulcers. Future studies need to identify the specific types of patients likely to obtain most benefit from treatment, in order to define more clearly the place of misoprostol in the treatment of these indications, as well as addressing the possibility of ulcer prevention with lower doses of misoprostol.

Perspective on the gastric antisecretory effects of misoprostol in man

Misoprostol, a synthetic prostaglandin E1 analog, has been found to be safe and effective for the treatment of peptic ulcer disease. This brief overview summarizes the gastric antisecretory effects of misoprostol in healthy human subjects using randomized, double-blind, placebo-controlled studies. Misoprostol effectively and dose-dependently inhibited basal gastric acid secretion at single doses of 50, 100 and 200 mcg/subject. Furthermore, misoprostol effectively inhibited meal-, histamine-, coffee- and tetragastrin-stimulated gastric acid secretion. The inhibition of meal-stimulated gastric acid secretion was not a consequence of the reduction of serum gastrin. In addition, misoprostol inhibited nocturnal gastric acid secretion. In these studies, the titratable acidity, volume, acid output and pepsin activity were inhibited by misoprostol. The extent of the secretory inhibition achieved with the 200 mcg dose of misoprostol was comparable to that of cimetidine administered at a 300 mg dose. The duration of the gastric antisecretory actions was in the order of 3 to 5 hours. We conclude that misoprostol is a potent inhibitor of gastric acid secretion in man.

Misoprostol clinical pharmacology. Establishment of activity in man

Misoprostol has been evaluated in healthy subjects for both antisecretory and pharmacological activity. Doses used were determined initially from acute and chronic tolerance testing in healthy subjects. In the single dosage range of 50-200 micrograms, misoprostol inhibits gastric acid secretion in a dose-related manner both in the basal state and after stimuli such as histamine and standard test meals. The 200 micrograms dose differs significantly from placebo as an antisecretory agent. A preliminary study in six subjects suggested that the 400 micrograms dose does not produce a substantial increase in activity over the 200 micrograms dose. Furthermore, side-effects such as diarrhea and abdominal cramps appear to be dose related. The antisecretory action of misoprostol is maximal one hour after drug administration and is negligible after 4-5 hours. These factors have until now dictated a 50-200 micrograms q.i.d. dosing regimen for misoprostol in clinical trials against peptic ulcer. Misoprostol does not significantly affect platelet function in terms of ADP-, collagen- and thrombin-induced platelet aggregation. Measurements of FEV1, vital capacity, and peak expiratory flow rate have revealed that misoprostol has no significant bronchodilating or bronchoconstricting effect. Studies of endocrine function revealed only a slight rise within the normal range in serum cortisol in women.

Interim results of a multicenter international comparison of misoprostol and cimetidine in the treatment of out-patients with benign gastric ulcers

An interim analysis has been performed of a multicenter randomized double-blind parallel-group comparison of misoprostol 50 micrograms (low dose), misoprostol 200 micrograms (high dose), and cimetidine 300 mg in out-patients with endoscopically diagnosed benign gastric ulcers. The drugs were administered q.i.d. for four weeks. Endoscopic assessments were made before treatment and at four weeks. Clinical assessments and laboratory tests were made before treatment and at two and four weeks. At the interim stage 421 subjects of the target 600 patients had been recruited by 22 principal investigators in 13 countries. Demographic data were similar for all groups with the exceptions of a lower proportion of males and smokers in the cimetidine group. Therapeutic success was defined as complete healing of all gastric ulcers. Cure rates at four weeks, for all eligible patients who received at least one dose of study medication (cohort 1), were significantly lower (P = 0.002) for misoprostol 50 micrograms (41.2%) than for misoprostol 200 micrograms (58.2%). There was no significant difference (P = 0.86) in cure rates between the high dose misoprostol and cimetidine (59.6%) groups. Cure rates were approximately 20% higher for non-smokers than smokers in both misoprostol groups, an effect not observed with cimetidine. In all three treatment groups the incidence of complaints, including diarrhea, was similar and therapy was well tolerated.