Omeprazole is a Superior Gastric Acid Suppressant in Cats

Summarised by Dr Liesel van der Merwe BSVC MMed(Vet)Med Small Animals

Parkinson K, Tolbert K, Messenger A et al. Evaluation of the Effect of Orally Administered Acid Suppressants on Intragastric pH in Cats.

Journal of Veterinary Internal Medicine. 2015(29) pp: 104 – 112

Why they did it?

Gastric acid suppressants including H2 receptor antagonists (H2RA) and proton pump inhibitors (PPIs) are the most widely prescribed medications for the adjunctive treatment of diseases which disrupt the gastric mucosal barrier in cats. Because of their small size and the fact that we are using human formulations – tablets need to be divided to achieve the correct dose. This study was designed to do 3 things: compare the effect of per os administered fractionated omeprazole tablets, reformulated omeprazole paste and famotidine on intra-gastric pH in cats, determine in which category of pH ( 0-1, 1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8 ) the pH was for the most time from days 4-7 of treatment and finally to evaluate the serum levels of omeprazole in the cats on bloods drawn on day 7 of treatment .

What they did:

Six healthy research colony cats with no evidence of GI disease were used. In a randomised open-label 4-way crossover design each cat was administered: placebo (250mg Lactose capsule per os bid), famotidine (0.88 – 1.26mg/kg per os bid), fractionated omeprazole tablets (0.88 – 1.26mg/kg per os bid or omeprazole reformulated paste (0.88 – 1.26mg/kg per os bid) for 7 days followed by a minimum 10 day washout period.

An omeprazole paste was reformulated using Gastroguard® to a suspension of 10mg/ml by mixing the paste with cod liver oil (1:39) and storing it at 7°C, away from light, to be used within 90 days.

On day 4 a Bravo™ pH capsule was fixed into the stomach endoscopically. Intra-gastric pH recordings were obtained telemetrically every 6 seconds for days 4 – 7 of treatment.

Blood samples were obtained from cats receiving omeprazole at 0.25, 0.5, 1, 2, 4, 6 and 8 hours after morning administration on day 7.

What they found:

The mean percentage time gastric pH is ≥3 and ≥4 has been found, using meta-analysis in humans , to be the ideal baseline for mucousal healing, with a goal in humans of being at this level for at least 75% and 67% of the day respectively. The table below summarises results for this parameter.


Placebo bid

Ranitidine bid

Omeprazole oid

Omeprazole bid

% time intra-gastric pH ≥ 3

16. ± 14.2%

42.7 ± 18.6%

68.4 ±35%

73.89 ± 23.2%

% time intra-gastric pH ≥ 4

9.6 ± 10.1%

22.4 ± 14.7%

57.8 ± 37.1%

55.7 ± 25.3%


Both omeprazole formulations, dosed bid, significantly increased intra-gastric pH compared to either the famotidine or the placebo (P<0.0001). No significant differences were found between the fractionated or reformulated omeprazole comparing the above parameter.

The area under the concentration –time curve (AUC), median and range has been shown to best reflect the inhibitory effects of omeprazole on gastric acid secretion and was similar between both formulations. The Tmax (time to maximum serum levels) was earlier in the paste formulation

Take home message:

These results suggest that either of the omeprazole formulations, dosed twice daily, provide significantly superior acid suppression in cats compared to famotidine (H2RA) or placebo. The fractionated enteric coated omeprazole tablet remains efficacious despite disruption of its enteric coating, and shows no significant difference to the reformulated omeprazole paste.

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