INTRAVENOUS BOLUS VERSUS CONTINUOUS-INFUSION OF FAMOTIDINE OR RANITIDINE ON 24 H INTRAGASTRIC ACIDITY IN FASTING HEALTHY-VOLUNTEERS

Infusions of H2-receptor antagonists may be clinically indicated to ma intain intragastric pH above 4 to reduce acute gastric mucosal lesions or to treat patients with bleeding peptic ulcers. Eight fasting healt hy volunteers were randomly assigned to receive ranitidine infusion al one (150 mg/day), ranitidine infusion plus 50 mg bolus injection of ra nitidine (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 col lected as half-hourly samples in which pH measurements were made. Meas ures 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 desig n of variance therapy; base pH before treatment administration in each crossover phase was employed as the covariant. Significant differenti al treatment means were tested by Newman-Keul's multiple range test at the 5% level of significance. The mean and median evening pH were hig her after famotidine than after ranitidine infusion, but all other pH readings were similar when using these doses. The addition of an initi al loading bolus of 50 mg ranitidine to the ranitidine infusion did no t result in any added differences in pH, whereas the addition of an in itial loading bolus of 40 mg famotidine to the famotidine infusion res ulted 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 loadi ng doses of ranitidine and famotidine were not equivalent in potency, and studies are needed to compare the potency of equivalent doses of r anitidine and famotidine when given by bolus plus infusion. Also the c linical relevance of these findings needs to be explored further in th e type of individuals potentially requiring intravenous H2-receptor an tagonists.