title: Xylazine-induced prolongation of gastrointestinal transit in dogs: reversal by yohimbine and potentiation by doxapram.
abstract: The effects of yohimbine and doxapram on xylazine-induced prolongation of gastroduodenal transit of barium sulfate were studied in 5 dogs. Base-line transit time was determined while the dogs were non-sedated and undisturbed; the time for barium sulfate to move from the stomach to the duodenojejunal junction was 5.6 +/- 4.0 minutes (mean +/- SD). An IV injection of xylazine (1 mg/kg) prolonged the transit time to 95.0 +/- 14.6 minutes. During the xylazine-induced prolongation of gastroduodenal transit, there were no vigorous gastric or intestinal peristaltic contractions for at least 60 minutes. Yohimbine, an alpha 2-adrenergic blocking agent, given IV at a dosage of 0.1 mg/kg, reversed the gastrointestinal and sedative effects of xylazine. Doxapram hydrochloride, an analeptic, given IV at a dosage of 5.5 mg/kg, prolonged the transit time to 43.0 +/- 22.8 minutes. When doxapram was given in combination with xylazine, it potentiated the gastrointestinal effect of xylazine, and further prolonged the transit time to 148.0 +/- 32.7 minutes. It was concluded that yohimbine is effective as an antidote to reverse the xylazine-induced prolongation of gastrointestinal transit, whereas doxapram has no value in this respect.
mesh_terms: D000818:Animals; D001466:Barium Sulfate; D004285:Dogs / Q000502:physiology*; D004315:Doxapram / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects*; D008297:Male; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D013843:Thiazines / Q000037:antagonists & inhibitors*; D014991:Xylazine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology*
chemical_list: D011942:Receptors, Adrenergic, alpha; D013843:Thiazines; D001466:Barium Sulfate; D014991:Xylazine; D015016:Yohimbine; D004315:Doxapram