TOLERANCE AND REBOUND TO H-2-RECEPTOR ANTAGONISTS - INTRAGASTRIC ACIDITY IN PATIENTS WITH DUODENAL-ULCER

Tolerance to the antisecretory effects of H-2-receptor antagonists develops consistently in healthy volunteers. The aim of this study was to determine whether tolerance occurs with repeated dosing of H-2-receptor antagonists in patients with duodenal ulcer. Continuous intragastric 24-hr pH measurements were performed in 12 patients with duodenal ulcer in symptomatic remission before, on days 1 and 29, and two days after receiving ranitidine 300 mg four times a day for 34 days. The 24-hr median intragastric pH (interquartile range) was 5.4 (4.4-6.1) on day 1 and 4.6 (4.0-5.2) on day 29 of dosing with ranitidine (not significant). Median nighttime pH was 6.8 (6.3-7.0) on day 1 and 6.8 (6.6-7.1) on day 29 (not significant). During the daytime, the median pH decreased marginally from 4.7 (3.8-5.2) on day 1 to 3.8 (3.0-4.6) on day 29 (P < 0.03). There was no difference in median intragastric pH during 24-hr, day and night periods before and two days after ranitidine dosing. No significant tolerance or rebound to H-2-receptor antagonists was observed in patients with duodenal ulcer disease. This contrasts with data gathered in healthy volunteers and may be due to defects in the regulation of acid secretion in duodenal ulcer disease.