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New research out of North Carolina State University is shedding some light on the ability of commonly used gastric acid suppressants
to increase gastric pH in dogs. The results of this study could affect how veterinarians manage gastric disease and protect
against gastric injury in dogs.
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 METHODS
Six 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.
STUDY FINDINGS
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.
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