title: In vivo and in vitro evaluation of the effects of domperidone on the gastrointestinal tract of healthy horses.
abstract: OBJECTIVE
  To determine the effects of domperidone on in vivo and in vitro measures of gastrointestinal tract motility and contractility in healthy horses.
  
  
  METHODS
  18 adult horses and tissue samples from an additional 26 adult horses.
  
  
  METHODS
  Domperidone or placebo paste was administered to healthy 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 6 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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  The potential beneficial effects of domperidone in horses with ileus need to be evaluated in horses with decreased gastric emptying or adynamic ileus.
authors.affiliation: Comparative Gastrointestinal Laboratory, Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, CA 95616, USA. jenieto@ucdavis.edu
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Nieto
authors.forename: Omar
authors.initials: O
authors.lastname: Maher
authors.forename: Scott D
authors.initials: SD
authors.lastname: Stanley
authors.forename: Richard
authors.initials: R
authors.lastname: Larson
authors.forename: Jack R
authors.initials: JR
authors.lastname: Snyder
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D004294:Domperidone / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D005769:Gastrointestinal Motility / Q000187:drug effects*; D041981:Gastrointestinal Tract / Q000187:drug effects*; D006736:Horses
chemical_list: D018492:Dopamine Antagonists; D004294:Domperidone