In vivo and in vitro evaluation of the effects of domperidone on the gastrointestinal tract of healthy horses.

This research article investigates the impact of the drug domperidone on the gastrointestinal movement and contractions in healthy horses, both in live animals and in extracted tissue samples.

Study Design and Participants

• The study was designed as a 2-period crossover study involving the use of a domperidone or placebo paste given to healthy adult horses.
• The experiment was carried out on 18 live horses, while tissue samples for observation were obtained from an additional 26 horses after they had been euthanized due to non-related medical issues.

Testing Methods

• Various tests were used to evaluate the effects of domperidone on the gastrointestinal functioning of the horses. First, gastric emptying was assessed in 12 horses after the administration of domperidone paste at two different dosages or a placebo paste. The evaluation was performed using the acetaminophen absorption test.
• In another group of six horses, the researchers looked at the effects of domperidone paste or placebo on defecation frequency, fecal moisture, the weight of feces produced, and stomach-to-anus transit time.
• The researchers also looked at how domperidone affected the contractile activity of smooth muscle in samples taken from different parts of the horse’s intestines: duodenum, jejunum, ileum, or colon.

Findings

• The administration of 5.0 mg of domperidone per kg increased the peak plasma acetaminophen concentration and area under the curve. This indicates an increase in gastric emptying.
• Conversely, a dosage of 1.1 mg of domperidone per kg had no significant effect on gastric emptying, fecal output, or transit time.
• Domperidone did not alter the contractile activities of the circular and longitudinal muscle strips from the duodenum, jejunum, ileum, or colon.
• The researchers also noticed that dopamine increased the contractile activity of longitudinal but not circular muscle strips from the midjejunum. However, domperidone inhibited this dopamine-induced contractile activity.

Interpretation and Implications

• The findings suggest that domperidone has the potential to increase gastric emptying in horses, but more research is needed to corroborate these results.
• Domperidone, however, did not affect fecal output, transit time or the contractile activities of most intestinal muscle strips, but it did decrease the dopamine-induced contractile activity of midjejunal longitudinal muscle strips.
• The potential beneficial effects of domperidone in horses with ileus (intestinal blockage or paralysis) remain uncertain, and the authors recommend further investigation in horses with reduced gastric emptying or adynamic ileus (a type of intestinal paralysis).