The effects of dose and diet on the pharmacodynamics of omeprazole in the horse

Sykes, B. W., Underwood, C., Greer, R., McGowan, C. M. and Mills, P. C. (2016) The effects of dose and diet on the pharmacodynamics of omeprazole in the horse. Equine Veterinary Journal, 49 4: 525-531. doi:10.1111/evj.12630

Author Sykes, B. W.
Underwood, C.
Greer, R.
McGowan, C. M.
Mills, P. C.
Title The effects of dose and diet on the pharmacodynamics of omeprazole in the horse
Journal name Equine Veterinary Journal   Check publisher's open access policy
ISSN 2042-3306
Publication date 2016-10-03
Year available 2016
Sub-type Article (original research)
DOI 10.1111/evj.12630
Open Access Status Not yet assessed
Volume 49
Issue 4
Start page 525
End page 531
Total pages 7
Place of publication Hoboken, United States
Publisher John Wiley & Sons
Language eng
Subject 3402 Equine
Abstract Background: Conflicting data are presented in the current literature regarding the efficacy of omeprazole for suppressing gastric acidity in the horse. Objectives: The objective of this study was to investigate the duration of intraday acid suppression achieved with two doses of omeprazole under two different dietary conditions. Study design: A four-way crossover design. Methods: Six adult Thoroughbred horses instrumented with percutaneous gastrotomy tubes were used. Intragastric pH was measured for continuous 23 h periods (08.00–07.00 h) for six consecutive days (Days 0–5). Baseline data was recorded on Day 0 and omeprazole administered on Days 1–5. Two doses (1 mg/kg and 4 mg/kg bwt per os once a day) and two diets (a high grain/low fibre [HG/LF] and ad libitum hay [HAY)] diet) were studied. Data for the percent (%) time pH was above 4 (%tpH>4) and median intraday pH was reported for two measurement locations and analysed using generalised estimating equations. Results: An effect of both diet and dose was evident with mean %tpH>4 and the mean of the median intraday pHs typically higher at the higher (4 mg/kg bwt) dose and in HG/LF diet. The overall efficacy of omeprazole in raising intragastric pH was good under the HG/LF conditions but relatively poor in the HAY diet. A cumulative effect of dosing, not previously reported in the horse, was observed. Conclusions: The overall efficacy of omeprazole in raising ventral gastric pH was less than previously reported. Both dose and diet may play a role in the efficacy of omeprazole in the horse. Therefore, the use of singular dosing recommendations that encompass all horse types and management conditions may not be appropriate and dosing recommendations that take into account the diet of the horse may be advantageous.
Keyword gastric
proton pump inhibitor
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
School of Veterinary Science Publications
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