Have You Heard? Omeprazole vs. famotidine: A modern peek at gastric acid suppression in dogs (script)
The oral acid suppressors famotidine and omeprazole have been widely used in people. While these medications are also commonly used by veterinarians, only omeprazole paste is veterinary-approved. The paste, designed and approved for use in horses, is of a higher concentration and has not been evaluated for use in dogs. Other experiments have shown omeprazole to be an effective acid suppressant in dogs, but details such as duration of effect and optimal dosing have not been determined. The coated tablets formulated for people are not ideal for use in dogs because they should not be crushed or broken, and this makes dosing difficult.
STUDY METHODSSix healthy adult dogs participated in this study. Each dog was treated with oral famotidine, an omeprazole tablet, omeprazole reformulated paste, and placebo for seven days with a 10-day washout period. To facilitate dosing, the omeprazole paste was combined with sesame oil at a ratio of 1:9. The doses of omeprazole tablets were about twice the commonly used dose because the tablets could not be broken. Therefore, the omeprazole paste and famotidine doses were increased twofold to ensure a consistent comparison among the drugs and formulations.
To determine the effects of the various gastric acid suppressants, the researchers used a catheterless radiotelemetric pH monitoring system used in human medicine—a new technique allowing for less invasive continuous pH monitoring. While anesthetized, each dog had a pH capsule inserted and attached directly to the gastrointestinal mucosa. These capsules transmitted continuous pH data to an external radiofrequency receiver. Plasma omeprazole concentrations were obtained on days one and seven of each treatment period, and the dogs were monitored daily for any adverse effects such as decreased appetite, vomiting, or fecal changes.
Even though higher doses of the gastric acid suppressants were used in this study, no significant adverse effects were noted. While episodes of vomiting were documented, they occurred with similar frequency in all groups, including the placebo group, and changes in fecal quality were most common during treatment with the omeprazole tablets.
Gastric pH was most strongly influenced by omeprazole; both the tablets and the paste produced similar results. The effect of omeprazole paste on pH began to wane 12 hours after administration. This waning effect may have been due to more rapid absorption and elimination of this formulation, leading the researchers to suggest twice-daily dosing if a reformulated omeprazole paste is used in dogs.
Perhaps the most interesting finding was that even at the higher dose given in this study, famotidine did not result in a significant increase in gastric pH. In fact, the results did not vary much from those of the placebo.
Tolbert K, Bissett S, King A, et al. Efficacy of oral famotidine and 2 omeprazole formulations for the control of intragastric pH in dogs. J Vet Intern Med 2011;25(1):47-54.
This "Have You Heard?" summary was provided by Avi Blake, DVM, a freelance technical editor and writer in Eudora, Kan.