Repeated Famotidine Administration Results in a Diminished Effect on Intragastric pH in Dogs.

Abstract

BACKGROUND: Famotidine is an acid suppressant commonly administered to dogs. Prolonged famotidine use in people results in decreased efficacy, but the effect in dogs is unknown. HYPOTHESIS/OBJECTIVES: To compare the effect of repeated oral administration of famotidine or placebo on intragastric pH and serum gastrin in dogs. We hypothesized that famotidine would have a diminished effect on intragastric pH on day 13 compared to day 1. ANIMALS: Six healthy adult colony Beagles. METHODS: Randomized, 2-factor repeated-measures crossover design. All dogs received oral placebo or 1.0 mg/kg famotidine q12h for 14 consecutive days. Intragastric pH monitoring was used to continuously record intragastric pH on treatment days 1-2 and 12-13. Mean pH as well as mean percentage time (MPT) that intragastric pH was &#x2265;3 or &#x2265;4 were compared between and within groups by analysis of variance. Serum gastrin was measured on days 0, 3, and 12 for each treatment. RESULTS: Continued administration of famotidine resulted in a significant decrease in mean pH, MPT &#x2265;3, and MPT &#x2265;4 (P < .0001) on day 12 and 13. This resulted in a mean decrease in pH by 1.63 on days 12 and 13 compared to days 1 and 2. Furthermore, a mean decrease of MPT &#x2265;3 and MPT &#x2265;4 by 33 and 45% was observed for the same time period, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Continued administration of famotidine results in a diminished effect on intragastric pH in dogs. Caution is advised when recommending long-term, daily oral administration of famotidine to dogs.