This study determined the effects of domperidone on the in vivo and in vitro measures of gastrointestinal tract motility and contractility in 18 healthy adult horses. The tissue samples of an additional 26 adult horses were also used.
Domperidone or placebo paste was administered to the horses in a 2-period crossover study. Gastric emptying was evaluated after oral administration of domperidone paste (1.1 or 5.0 mg/kg) or placebo paste by means of the acetaminophen absorption test in 12 horses. Frequency of defecation, weight of feces produced, fecal moisture and stomach-to-anus transit time of microspheres were evaluated after administration of domperidone paste (1.1 mg/kg) or placebo paste in six horses. The effect of domperidone on smooth muscle contractile activity in samples of duodenum, jejunum, ileum or colon obtained from 26 horses immediately after euthanasia (for nonsystemic medical problems) was investigated.
Oral administration of 5.0 mg of domperidone/kg increased peak plasma acetaminophen concentration and area under the curve, indicating increased gastric emptying. Administration of 1.1 mg of domperidone/kg had no effect on gastric emptying, transit time, defecation frequency or amount and moisture of excreted feces. Contractile activities of circular and longitudinal muscle strips from the duodenum, jejunum, ileum or colon were not altered by domperidone. Dopamine increased contractile activity of longitudinal muscle strips but not that of circular muscle strips from the midjejunum. Domperidone decreased the dopamine-induced contractile activity of midjejunal longitudinal muscle strips.
The potential beneficial effects of domperidone in horses with ileus need to be evaluated in horses with decreased gastric emptying or adynamic ileus.
Source: Jorge E. Nieto et al., 2013. In vivo and in vitro evaluation of the effects of domperidone on the gastrointestinal tract of healthy horses. AJVR online, August 2013. doi: 10.2460/ajvr.74.8.1103