Systemic morphine administration causes gastric distention and hyperphagia in healthy horses.

BACKGROUND

There are no data investigating the effect of systemic morphine on the size of the stomach or the food consumption in horses.

OBJECTIVES

To evaluate gastrointestinal side effects of morphine administered systemically in healthy horses by the means of clinical and ultrasonographic evaluations.

STUDY

DESIGN

In vivo experiment.

METHODS

On day 1 of the experiment, six healthy French Trotter mares were evaluated clinically and an abdominal ultrasonography was performed three times 4 h apart to record the size of the stomach, the number of contractions per minute of the duodenum, jejunum, caecum, left and right ventral colons. On Day 2, morphine was administered three times 4 h apart at the dose of 0.1 mg/kg i.v. and the same ultrasonographic examinations performed. On Day 3, only clinical and ultrasonographic examinations were performed as on Day 1. Amounts of hay and water ingested, frequency and weight of faeces were recorded throughout the study.

RESULTS

Number of contractions of the duodenum, caecum, left and right ventral colons were significantly decreased after morphine administration. Size of the stomach was increased significantly with a cumulative effect of repeated doses of morphine. Hay (+0.4 kg/h, P<0.001) and water (+1.1 L/h, P<0.001) consumption were significantly increased.

MAIN LIMITATIONS: The study was performed in healthy horses.

CONCLUSIONS

Systemic morphine administration causes gastrointestinal depression, gastric distention and hyperphagia in horses. Clinical and ultrasonographical examinations are valuable tools to identify side effects of morphine administration in horses. Further studies are needed to assess side effects and monitoring in clinically painful cases. Horses receiving systemic morphine administration should be closely monitored for signs of gastric distention and, specifically, the amount of food given while receiving treatment should be controlled to avoid complications.