Continuous 24 hour intragastric pH monitoring: focus on reproducibility in duodenal ulcer patients. A preliminary report.

Continuous 24 h intragastric pH monitoring is increasingly recommended for deciding which is the most appropriate regimen and dosage of new gastric antisecretory drugs. In order to assess its reproducibility, we have repeated the test twice on consecutive days in six patients with endoscopically proven duodenal ulcers because this type of patient seems to be the most suitable for studies on the efficacy of the above mentioned therapy. No patient received medication during the two examination days. Our data showed there was no significant difference (t = 0.31, p = 0.76) between the 24 h areas under the curve of pH profiles of the first day compared with those of the second (mean +/- SD : 3.152 +/- 681 vs 3.073 +/- 1,122). The lack of significant difference (p = 0.20) between the mean times elapsed at the various pH levels during the first and second days was further proof of the reproducibility of the method. As wells these results suggest that day-to-day reproducibility of the technique is good in duodenal ulcer patients. Therefore, its repeated use on the same patient to investigate the effects of various drugs and their different dosages on gastric acidity appears to be reliable.

Continuous 24-hour intragastric pH monitoring in the evaluation of the effect of a nightly dose of famotidine, ranitidine and placebo on gastric acidity of patients with duodenal ulcer.

In 11 duodenal ulcer patients, the antisecretory effects of bedtime famotidine 40 mg were compared to those obtained with ranitidine 300 mg and placebo by means of continuous 24-hour intragastric pH monitoring. The 24-hour areas under the curve of pH profiles of the two H2 blockers were significantly different from those related to placebo (p approximately 0 for ranitidine and p = 0.00001 for famotidine), but not from each other (p = 0.51). Onset and duration of the famotidine action, however, were respectively earlier and longer lasting (12 vs. about 9 h) than those of ranitidine. Famotidine was also significantly superior (p approximately 0) to ranitidine in keeping intragastric pH at high values (especially those comprised between 6 and 8 pH units), although theoretically equipotent doses of the two H2 antagonists were used.

24-H comparison between pH values of continuous intraluminal recording and simultaneous gastric aspiration.

This study was undertaken to show whether the correlation between pH values indicated by an intraluminal pH electrode and those simultaneously recorded for gastric aspirates is not only linear but also proportional, so that the two measurement techniques can be considered alternative. A 24-h intragastric pH-monitoring with an antimony electrode, to which a nasogastric tube for hourly aspiration of gastric juice was closely attached, was performed on 20 duodenal ulcer patients. Our data show that the slope of the straight line related to 335 pH pairs is virtually equal to 1, whereas the elevation is almost equal to zero, and this result strongly suggests that a proportional relationship exists between intragastric and aspirate pH levels throughout the whole 24-h period. Besides, in the majority of cases (81%) the pH pairs differ by no more than 1 pH unit. It can be concluded that these two pH monitoring methods may be alternative.

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.