Intragastric pH monitoring during antisecretory therapy in patient with gastrointestinal bleeding.

This study was undertaken to evaluate the effect of various cimetidine and ranitidine administration schedules on intragastric pH in patients with recent episodes of hematemesis. The investigation was performed on 10 subjects whose hemorrhage had ceased either spontaneously or after pharmacological treatment for at least 24-36 h. The following therapeutic regimens were randomly evaluated: bolus infusions of ranitidine (100 mg/6 h and 50 mg/4 h) and cimetidine (400 mg/6 h and 200 mg/4 h) and continuous infusions of ranitidine (0.2 and 0.4 mg/kg/h) and cimetidine (100 mg/h). Each study evaluated at least two consecutive boli or an 8-h continuous infusion. All treatments produced significant elevations in the basal intragastric pH (p less than 0.001). With bolus administrations, however, the pH displayed consistent oscillations. The pH fell below 4 approximately 6 h after the administration in all the patients treated with 400 mg of cimetidine and in three treated with 50 mg of ranitidine. The administration of histamine H2-receptor antagonists every 4 h allowed better control of intragastric acidity. The pH dropped below 4 in seven of the 10 patients in the 4-h period after the administration of 200 mg cimetidine, and in one of the 10 patients treated with 50 mg of ranitidine/4 h. Increasing bolus dose did not reduce the time lapse or increase the inhibition of intragastric acidity. Continuous infusions were efficacious in maintaining pH values constantly above 6. Ranitidine (0.2 mg/kg/h) achieved the same inhibitory efficiency as cimetidine (100 mg/h). These data indicate that continuous venous infusion of both ranitidine and cimetidine is significantly more efficacious than repeated single bolus administrations.