Evaluation of antisecretory activity of misoprostol in duodenal ulcer patients using long-term intragastric pH monitoring

The effect of the new synthetic prostaglandin E1 analog, misoprostol, on intragastric acidity was evaluated by means of 24-hr intraluminal pH monitoring of 16 duodenal ulcer patients. They were randomly allocated into two groups: eight received no medication and misoprostol 400 micrograms bid and eight received ranitidine 150 mg and misoprostol 400 micrograms bid not less than one week apart. The comparison of the 24-hr areas under the curve related to the median pH values showed that no difference existed between misoprostol and untreated patients in the first group, while ranitidine was significantly more effective (P = 0.00003) than misoprostol in the second group. The analysis of arithmetic differences between the 24-hr median pH values showed that misoprostol increased pH values by at least one unit compared to the untreated subgroup for about 3.5 hr, while the antisecretory action of ranitidine was far superior to that of misoprostol throughout the whole 24-hr period. It can be concluded that the effect of twice daily doses of misoprostol 400 micrograms on 24-hr intragastric pH is small and not at all comparable to that of the well-known potent H2 blocker ranitidine.