A double-blind study of prophylactic effect of misoprostol on lesions of gastric and duodenal mucosa induced by oral administration of tolmetin in healthy subjects

Prostaglandin treatment for peptic ulcer

Prostaglandin analogues have been expected to outperform other antisecretory drugs as ulcer healing agents. This expectation arises from their ability to combine 'cytoprotection' with gastric secretory inhibition. Evidence of the existence of these two separate functions abounds in animals and in humans, but a clinical advantage has not evolved. Whereas most clinical trials show no difference between prostaglandin analogues and H2-receptor antagonists, some studies have shown the prostaglandins to be significantly less effective or no better than placebo. The role of cytoprotection in ulcer healing (as opposed to prevention) may be questioned and the present clinical role for these agents is unclear.

Prostaglandins, H2-receptor antagonists and peptic ulcer disease

Peptic ulcer develops when offensive factors overwhelm defensive processes in the gastroduodenal mucosa. Offensive factors include NSAIDs, hydrochloric acid-peptic activity, bile reflux, and some products of the lipoxygenase pathway such as leukotriene B4; whereas defensive processes are largely mediated by prostaglandins through poorly understood mechanisms uniformly termed cytoprotection. Cytoprotection, a physiological process working through the products of arachidonic acid metabolism, may result from the net effect of the protective actions of prostaglandins versus the damaging actions of leukotrienes. Some prostaglandins also have antisecretory effects. Therefore the peptic ulcer healing effects of prostaglandin analogues, all of which have significant antisecretory activity, may be more due to their antisecretory effects than primarily to their effects on mucosal defences. Certain drug-induced gastroduodenal lesions, e.g. NSAID-induced ulcers, which are often unresponsive to H2-receptor antagonists, have been healed and their recurrence prevented by the use of PGE1 and PGE2 analogues. All the prostaglandin analogues investigated to date in humans have the potential for inducing abortion, an important side effect which may limit their worldwide use. The optimal prostaglandin analogue for ulcer healing should not induce abortion and should be potently cytoprotective. The predominant damaging agent in the development of peptic ulcer disease is gastric hydrochloric acid. Thus, the worldwide established efficacy and safety of H2-receptor antagonists such as cimetidine, ranitidine, famotidine and most recently of roxatidine acetate suggest that these agents have become the standard by which other forms of anti-ulcer therapy should be judged.

Review: acute human models of gastric mucosal injury

The use of acute human models of gastric mucosal injury has been stimulated by a need to understand more fully the problems of non-steroidal anti-inflammatory drugs but such models have other applications. None is ideal and they all share certain drawbacks. For none of them has a precise relationship to clinical events been established and they have all tended to be employed on a population of young healthy subjects who are not those at greatest clinical risk. Of individual methods mucosal potential difference is an indirect measure which is too often affected by other influences to be acceptable as a measure of mucosal injury when used alone, although it has some value as an adjunct to other measurements. Assay of DNA in gastric washings is a suitable technique for quantifying desquamation of gastric epithelial cells occurring in response to acute injury; on present evidence its significance is much more difficult to assess in the context of continuing challenge over several days. By contrast, measurement of microbleeding is more suitable for quantifying injury over several days of NSAID ingestion; little bleeding is recorded with a single acute challenge. Endoscopy can demonstrate macroscopic lesions which result from mucosal injury--injury which is quantified more easily and sensitively by measurements of cellular exfoliation or bleeding. Paradoxically, endoscopy's strength has been to underline the scientific weakness of acute models because it shows that it is rare for ulcers, which are the lesions of clinical concern to develop in these studies.

Protection by misoprostol against naproxen-induced gastric mucosal damage

The protective effect of misoprostol against naproxen-induced gastric mucosal damage was the subject of a double-blind, randomized, parallel-group study. Thirty-two healthy subjects were treated with naproxen 500 mg twice daily and either misoprostol 200 micrograms or matching placebo twice daily for seven days. Gastroscopy was performed before and after the treatment period and the mucosa was assessed for erosive and petechial lesions according to a predetermined scoring scheme. Of 25 evaluable subjects, 12 were treated with misoprostol and 13 were treated with placebo. The mean overall endoscopic score was 1.24 +/- 0.09 with placebo and 0.26 +/- 0.07 with misoprostol. The difference, 0.98, was highly significant (p less than 0.001), with 95 percent confidence limits of 0.74 to 1.22. All subjects in the placebo group had higher mean scores than any in the misoprostol group. The scores for erosive and bleeding lesions in the antrum and corpus/fundus of the stomach were all reduced by administration of misoprostol. In conclusion, the results clearly demonstrate that misoprostol protects the gastric mucosa of humans against naproxen-induced damage.

Comparative efficacy of misoprostol and cimetidine in the treatment of acute duodenal ulcer. Results of major studies

Misoprostol, a synthetic methyl ester of prostaglandin E1, has been shown to possess potent antisecretory activity in addition to a mucosal protective effect. Several multicenter double-blind, placebo-controlled trials confirmed the efficacy of misoprostol in the treatment of duodenal ulcer when administered at 800 micrograms in two or four divided doses daily. This report summarizes three cimetidine-controlled trials conducted in three separate geographic areas (Europe, Argentina, and Japan). The trials were double blind, randomized, and endoscopically controlled. In all studies, healing was defined as the absence of ulcer on endoscopy. The efficacy of misoprostol in the treatment of duodenal ulcer was shown to be equivalent to that of the histamine H2-receptor antagonist. In the Argentine study, the rate of disappearance of mucosal erosions was significantly greater for misoprostol than for cimetidine. Misoprostol was well tolerated. Mild and transient diarrhea not necessitating treatment or withdrawal occurred in 4 to 9 percent of the misoprostol-treated patients. These results indicate that misoprostol has a unique anti-ulcer action and represents a significant addition to the physician's armamentarium in the total medical management of duodenal ulcer.

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.

Gastric protection by misoprostol against 1,300 mg of aspirin. An endoscopic dose-response study

Misoprostol at a dose of 200 micrograms inhibits gastric acid secretion and protects the gastric mucosa against the injurious effects of a single 1,300-mg dose of aspirin. The purpose of this study was to determine whether lower subantisecretory doses of misoprostol protect the gastric mucosa in this single-dose aspirin model. Protection was defined as no more than 10 hemorrhagic spots and no more than two hemorrhagic streaks. A total of 140 men participated in the two phases of the study. In the first phase, groups of 10 subjects each received placebo or misoprostol in doses of 200 micrograms, 100 micrograms, 50 micrograms, or 25 micrograms in a double-blind design. All misoprostol doses protected 50 to 70 percent of subjects as compared with 20 percent of subjects in the placebo group. To expand the number of observations, 90 additional subjects in groups of 30 each were evaluated after receiving misoprostol 50 micrograms or 25 micrograms or placebo. Misoprostol 50 micrograms protected 14 of 30 subjects (47 percent), 25 micrograms protected 11 of 30 (37 percent), and placebo protected six of 30 (20 percent). The dose-response trend was statistically significant (p less than 0.05). It is concluded that misoprostol protects the gastric mucosa against a single 1,300-mg dose of aspirin and that there is a significant dose-response relationship.

Overview of the mucosal protective effects of misoprostol in man

Misoprostol, a novel synthetic analog of prostaglandin E1 has been evaluated for its potential mucosal protective properties in healthy human subjects using randomized, double-blind, placebo-controlled studies. Misoprostol significantly reduced established aspirin-induced gastric microbleeding. Likewise, misoprostol significantly inhibited aspirin-induced fecal blood loss when administered concurrently with aspirin. The reduction of gastrointestinal blood loss was neither a consequence of the inhibition of gastric secretion, nor a change in aspirin absorption. In addition, misoprostol effectively attenuated the transmucosal potential difference drop induced by sodium taurocholate. In endoscopic studies, misoprostol significantly inhibited damage to the gastroduodenal mucosa induced by aspirin, tolmetin and ethanol. In the ethanol study, the protective effects of misoprostol were significantly and profoundly greater than that afforded by cimetidine administered at an effective gastric antisecretory dose. These studies indicate that misoprostol has mucosal protective property in man. The basis for this mucosal protective effect is not fully known, but laboratory and clinical evidence indicate a direct effect on the barrier functions of the stomach, an increased or maintenance of gastric mucosal blood flow and an enhanced mucus and bicarbonate secretion. The implications of these findings suggest that misoprostol may be useful in the prevention and treatment of acute gastroduodenal mucosal lesions and inflammation.

Effects of misoprostol on human circulation

Prostaglandins (PGs) of the E-type are potent vasodilators in most species and in most vascular beds. However, vasoconstrictor effects of PGEs have also been noted at selected sites. This study examined the effects of misoprostol, a PGE1 analog with antiulcer activity, on the human cardiovascular system. Twenty healthy subjects participated in this double-blind, placebo-controlled, parallel group study. Following a 12 hour fast, heart rate, arterial blood pressure, light reflex plethysmography of the finger, resting blood flow volume in the lower arm and leg and peripheral vascular resistance were measured at 10 min. intervals for 1 hour prior to drug administration, to permit calculating baseline values. Misoprostol (400 mcg) or its matching placebo were administered orally, and the measurements were repeated at 10 min. intervals over the next 2 hours. A decrease in leg blood flow volume and a corresponding increase in leg peripheral vascular resistance were noted in the misoprostol group. A statistically significant decrease in heart rate between the two treatment groups was also noted. These small changes were not considered to be of clinical importance. No adverse experiences were reported. In conclusion, a single dose of misoprostol (400 mcg) has no clinically significant vasoconstrictive or vasodilative properties in man.

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.

The role of arachidonic acid metabolites in gastrointestinal homeostasis. Biochemical, histological and clinical gastrointestinal effects

Metabolites of arachidonic acid have a broad range of physiological functions in the gastrointestinal tract, and seem to be involved in certain disturbances of gastrointestinal integrity and function. Prostaglandins inhibit gastric acid secretion, apparently via an adenylate cyclase-linked receptor, and also stimulate bicarbonate and mucus production by alternative mechanisms. These are all beneficial in treating gastroduodenal ulceration. Moreover, clinical studies have revealed deficient prostaglandin synthesis in the gastric and duodenal mucosa of patients with gastrointestinal ulcers, which suggests that endogenous prostaglandins have a protective role in the gastrointestinal tract. In animal studies, prostaglandin analogues have been shown to protect the gastric mucosa from damage induced by various potent irritants, and this protection seems to involve the deeper layers of the mucosa as well as the epithelium. Indeed, misoprostol and other prostaglandin analogues have proved therapeutically effective in treating gastroduodenal ulceration. Prostaglandins also influence intestinal motility and fluid movement. Prostaglandin E derivatives generally relax circular smooth muscle, contract longitudinal smooth muscle and increase fluid secretion into the intestinal lumen. As a result of these effects, prostaglandins may cause diarrhoea. There is also evidence that prostaglandin synthesis is increased in patients with diarrhoea. Finally, it has been reported that tissue concentrations of prostaglandins are increased in patients with ulcerative colitis, but it is unclear if this is a primary cause, or secondary event. Significantly greater conversion of arachidonic acid to its metabolites was recorded in the mucosa of patients with inflammatory bowel disease compared with the mucosa of healthy subjects. This included a substantial increase in the concentration of leukotriene B4.(ABSTRACT TRUNCATED AT 250 WORDS)

Misoprostol prevents damage to the gastric mucosa by stabilizing the mast cells

Prostaglandins have been shown to prevent the damage to the gastric and intestinal mucosa which has been induced by diverse necrotizing substances. These damaging stimuli increase the liberation of histamine from mast cells. Because of its well known effects on cellular permeability, histamine may serve the initial stimulus for mediating cellular damage. The aim of our study was to investigate the effect of misoprostol, a synthetic PGE1 analog, on tissue histamine concentration and mast cell counts after damage to the gastric mucosa induced by stress, histamine, aspirin and concentrated ethanol in guinea pigs. Misoprostol or its matching placebo were administered intragastrically 3 minutes prior to the ulcerogenic stimulus. After the induction of the injury, the animals were sacrificed, stomachs were examined for ulceration. Gastric and duodenal histamine concentrations were determined. Mast cells from these organs were stained and counted. All four ulcerogenic stimuli resulted in significant gastric ulcer formation. This ulcerogenic action was accompanied by a significant decrease in mucosal histamine concentration and mast cell counts. Misoprostol induced a dose-dependent inhibition of gastric damage, histamine depletion and mast cell destruction. These results indicate that the stabilization of mast cells by misoprostol is an important mechanism for its mucosal protective effects against ulcerogens.

Prostaglandins in peptic ulcer disease. An overview of current status and future directions

Naturally occurring prostaglandins almost certainly play an important role in maintaining the integrity of the gastrointestinal mucosa. Clinical evidence available to date indicates that synthetic analogues of prostaglandins heal gastroduodenal ulcer only in doses that suppress gastric acid. However, non-antisecretory doses of prostaglandins may eventually have a role in the treatment of ulcer disease by maintaining ulcer healing and preventing recurrence. This possibility along with the potential of prostaglandins to prevent gastroduodenal mucosal injury caused by NSAIDs, alcohol, aspirin and stress, if supported by the results of ongoing clinical trials, may prove to be a major therapeutic advance for the treatment of acid peptic disease.

Overview of misoprostol clinical experience

Misoprostol is an E1 prostaglandin analog. Most of the other synthetic prostaglandins that are being studied in advanced clinical trials for gastrointestinal diseases are E2 derivatives. Misoprostol has shown a dose-related antisecretory effect that lasted 3-5.5 hr. In addition, animal studies have shown cytoprotective properties that are being confirmed in clinical studies. Ulcer-healing trials using four times daily dosing appear to parallel the antisecretory dose-response curve up to a dose of 200 micrograms qid. Evidence presented in this supplement suggests a further increase in healing-rate response at 300 micrograms misoprostol qid. The misoprostol healing rates obtained in duodenal ulcer and gastric ulcer therapy at 200 micrograms qid are not significantly different from those seen in the same studies with cimetidine at a dose of 300 mg qid. No significant rebound in recurrence has been observed during follow-up for 12 months after short-term 100- and 200-micrograms qid misoprostol treatment. The most frequent adverse effects are dose-related diarrhea and abdominal cramping, which are transient in most patients and have not caused a significant problem in clinical use. There is also a tropic effect on the pregnant uterus, which was observed in a special pharmacologic clinical study. No significant abnormalities have been detected in clinical laboratory tests or gastric biopsies. There have also been no adverse effects noted on blood pressure, pulse, platelets, the immune system, pulmonary function, gastrointestinal hormones, or the endocrine system. These previously discussed characteristics of misoprostol, and current data, suggest that this prostaglandin E1 derivative may be an important addition to the treatment of peptic ulcer disease.

A multicenter international controlled comparison of two dosage regimens of misoprostol with cimetidine in treatment of gastric ulcer in outpatients

In this double-blind, parallel-group multicenter study, patients with endoscopically proven gastric ulcers were randomly allocated to treatment with either 50 micrograms or 200 micrograms of misoprostol or 300 mg of cimetidine, each given four times daily for four weeks. Endoscopic, clinical and laboratory assessments were made before treatment and after four weeks; clinical and laboratory assessments were repeated at two weeks. In the Korean center, assessments were also made after six weeks and at eight weeks of treatment. Six hundred and thirty patients were studied. The three treatment groups were similar in age and occupation. However, the proportion of men in the misoprostol 50-micrograms, 200-micrograms and cimetidine 300-mg groups was 67%, 63%, and 59%, respectively. Therapeutic success was defined as complete healing of all ulcers, judged endoscopically. On an intent-to-treat basis, which includes all losses to follow-up and withdrawals as treatment failures, ulcer healing rates in the misoprostol 50-micrograms, 200-micrograms and cimetidine 300-mg groups were 39%, 51%, and 58%, respectively. In the Korean center, the healing rates were 38%, 64%, and 70%, respectively, after eight weeks of treatment. There was no statistically significant difference in the healing rates at four weeks between the misoprostol 200-micrograms and cimetidine 300-mg groups (P = 0.16). The healing rate with the misoprostol 200-micrograms dose was significantly better than with the 50-micrograms dose (P = 0.008). Cimetidine 300 mg relieved global pain significantly better than misoprostol 200 micrograms at two weeks (P = 0.047) but not at four weeks.(ABSTRACT TRUNCATED AT 250 WORDS)