The Effect of Orally Administered Ranitidine and Once-Daily or Twice-Daily Orally Administered Omeprazole on Intragastric pH in Cats

Background: Gastric acid suppressants frequently are used in cats with acid-related gastric disorders. However, it is not known if these drugs effectively increase intragastric pH in cats. Objectives: To examine the effects of PO administered ranitidine and omeprazole on intragastric pH in cats and to compare the efficacy of once-daily versus twice-daily dosage regimens for omeprazole. Animals: Eight domestic shorthair cats. Methods: Using a randomized 4-way cross-over design, cats were given enteric-coated omeprazole granules (1.1-1.3 mg/kg q24h and q12h), ranitidine (1.5-2.3 mg/kg q12h), and placebo. Intragastric pH was monitored continuously for 96 hours using the Bravo TM system a, starting on day 4 of treatment, followed by a median washout period of 12 days. Mean percentage of time pH was >= 3 and >= 4 was compared among groups using repeated measures ANOVA. Results: Mean +/- SD percentage of time intragastric pH was >= 3 and >= 4 was 67.0 +/- 24.0% and 54.6 +/- 26.4% for twice-daily omeprazole, 24.4 +/- 22.8% and 16.8 +/- 19.3% for once-daily omeprazole, 16.5 +/- 9.0% and 9.6 +/- 5.9% for ranitidine, and 9.4 +/- 8.0% and 7.0 +/- 6.6% for placebo administration. Twice-daily omeprazole treatment significantly increased intragastric pH, whereas pH after once-daily omeprazole and ranitidine treatments did not differ from that of placebo-treated cats. Conclusion and Clinical Importance: Only twice-daily PO administered omeprazole significantly suppressed gastric acidity in healthy cats, whereas once-daily omeprazole and standard dosages of ranitidine were not effective acid suppressants in cats.