The frequency of oral famotidine administration influences its effect on gastric pH in cats over time

BACKGROUND: Famotidine is commonly administered to cats. Prolonged famotidine administration results in decreased efficacy in humans, dogs, and cows, but the long‐term effects in cats are unknown. OBJECTIVES: To compare the effect of 2 oral administration frequencies of famotidine, twice daily (Group 1) and twice daily every second day (Group 2), on intragastric pH and serum gastrin concentrations in cats. We hypothesized a diminished effect on intragastric pH would be observed over time in Group 1 but not Group 2. ANIMALS: Sixteen healthy cats. METHODS: Randomized, 2‐factor repeated measures crossover design. Cats received 0.5‐1.24 mg/kg (median, 0.87 mg/kg) famotidine twice daily or twice daily every second day for 14 consecutive days. Intragastric pH monitoring was used to record intragastric pH on treatment days 1‐3 and 11‐13. Mean pH and mean percentage time (MPT) intragastric pH was ≥3 and 4 were compared between and within treatment groups by analysis of variance. RESULTS: Significant treatment group by time interactions were observed for mean intragastric pH, MPT intragastric pH ≥3 and 4 (P = .009, P = .02, P = .005, respectively). Interaction post hoc tests identified significant decreases in mean intragastric pH (P = .001), MPT ≥3 (P = .001), and MPT ≥4 (P = .001) on day 13 compared to day 1 in Group 1 but not in Group 2. CONCLUSIONS AND CLINICAL IMPORTANCE: Oral famotidine administration results in a diminished effect on intragastric pH in healthy cats when given twice daily every day.