Abstract
Infusions of H2-receptor antagonists may be clinically indicated to maintain intragastric pH above 4 to reduce acute gastric mucosal lesions or to treat patients with bleeding peptic ulcers. Eight fasting healthy volunteers were randomly assigned to receive ranitidine infusion alone (150 mg/day), ranitidine infusion plus 50 mg bolus injection of ranitidine (total of 200 mg/day), famotidine infusion alone (40 mg/day) or famotidine infusion plus 40 mg bolus injection of famotidine (total of 80 mg/day). Gastric fluid contents were aspirated for 24 h and collected as half-hourly samples in which pH measurements were made. Measures analyzed were mean and median pH, percentage pH at or below 3, 4 or 5 for the 24 h period, daytime, evening and nighttime. The data for each of the variables were analyzed as a Latin square crossover design of variance therapy; base pH before treatment administration in each crossover phase was employed as the covariant. Significant differential treatment means were tested by Newman-Keul’s multiple range test at the 5% level of significance. The mean and median evening pH were higher after famotidine than after ranitidine infusion, but all other pH readings were similar when using these doses. The addition of an initial loading bolus of 50 mg ranitidine to the ranitidine infusion did not result in any added differences in pH, whereas the addition of an initial loading bolus of 40 mg famotidine to the famotidine infusion resulted in a higher 24 h median pH, as well as a lower percentage of pH values of 4 or below, 16.6% versus 28.5%, P<0.05. However, the loading doses of ranitidine and famotidine were not equivalent in potency, and studies are needed to compare the potency of equivalent doses of ranitidine and famotidine when given by bolus plus infusion. Also the clinical relevance of these findings needs to be explored further in the type of individuals potentially requiring intravenous H2-receptor antagonists.