Systemic morphine administration causes gastric distention and hyperphagia in healthy horses.
Authors: Tessier C, Pitaud J-P, Thorin C, Touzot-Jourde G
Journal: Equine veterinary journal
Summary
# Editorial Summary: Morphine-Induced Gastric Changes in Horses Whilst morphine is commonly used for pain management in equine practice, little was known about its effects on gastrointestinal function and feeding behaviour. Tessier and colleagues administered intravenous morphine (0.1 mg/kg) to six healthy mares at four-hourly intervals over 24 hours, using ultrasonography to measure gastric size and intestinal motility alongside detailed monitoring of hay and water intake, defaecation frequency and faecal weight. The findings revealed a concerning dose-dependent increase in gastric distention coupled with significant depression of duodenal and colonic contractions; notably, horses consumed substantially more hay (+0.4 kg/h) and water (+1.1 L/h) during morphine administration, indicating opioid-induced hyperphagia. For practitioners managing acutely painful horses requiring systemic opioids, these results underscore the critical importance of restricting forage intake during treatment and implementing close clinical monitoring to prevent secondary gastric complications; further investigation in clinically affected horses is warranted to determine whether these effects persist with prolonged use or differ between routes of administration.
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Practical Takeaways
- •Horses receiving systemic morphine require close monitoring for gastric distention and should have food intake strictly controlled to prevent complications
- •Be aware that morphine administration will increase appetite and water consumption despite causing gastrointestinal dysfunction, making dietary management critical during treatment
- •Clinical signs of gastric distention may develop with repeated morphine dosing; consider alternative analgesia or enhanced monitoring protocols when systemic morphine is necessary
Key Findings
- •Systemic morphine (0.1 mg/kg i.v.) caused significant gastric distention with cumulative effects from repeated doses
- •Morphine significantly decreased duodenal, caecal, and colonic contractions indicating gastrointestinal depression
- •Hay consumption increased by 0.4 kg/h (P<0.001) and water consumption increased by 1.1 L/h (P<0.001) during morphine treatment
- •Ultrasonography proved valuable for identifying morphine-related gastrointestinal side effects in horses