title: Use of yohimbine to reverse prolonged effects of xylazine hydrochloride in a horse being treated with chloramphenicol.
abstract: A 1-year-old Standardbred gelding had received xylazine hydrochloride (0.75 to 1.00 mg/kg [0.34 to 0.45 mg/lb] of body weight, IV) during 2 surgeries for debridement of a wound. The horse was given chloramphenicol (55 mg/kg [25 mg/lb], PO, q 6 h) for 5 days, and was anesthetized a third time with xylazine (0.75 mg/kg, IM). Five hours after administration of xylazine, the horse remained markedly sedated and had clinical signs of gaseous distention of the large bowel (bloat) requiring trocharization. Administration of yohimbine (0.03 mg/kg [0.01 mg/lb], i.v.) eliminated signs of sedation within 5 minutes. Moderate flatulence developed, and gastrointestinal sounds could be heard within all 4 abdominal quadrants within 15 minutes of yohimbine administration. The remainder of recovery was unremarkable. Xylazine induces bradycardia and decreases gastrointestinal motility in addition to causing sedation, muscle relaxation, and analgesia. Chloramphenicol can inhibit oxidase activity of cytochrome P-450 and inhibit metabolism and elimination of drugs such as xylazine.
authors.affiliation: Department of Veterinary Clinical Medicine, College of Veterinary Medicine, Ohio State University, Columbus 43202, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Grubb
authors.forename: W W
authors.initials: WW
authors.lastname: Muir
authors.forename: A L
authors.initials: AL
authors.lastname: Bertone
authors.forename: L A
authors.initials: LA
authors.lastname: Beluche
authors.forename: M
authors.initials: M
authors.lastname: Garcia-Calderon
mesh_terms: D000771:Anesthesia, Intravenous / Q000379:methods / Q000662:veterinary; D000777:Anesthetics / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002701:Chloramphenicol / Q000494:pharmacology / Q000627:therapeutic use*; D065607:Cytochrome P-450 Enzyme Inhibitors; D003646:Debridement / Q000379:methods / Q000662:veterinary; D004347:Drug Interactions; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology; D006736:Horses / Q000378:metabolism / Q000502:physiology* / Q000601:surgery; D008297:Male; D013565:Sympatholytics / Q000494:pharmacology*; D013710:Tendons / Q000601:surgery; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology; D014991:Xylazine / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology*
chemical_list: D000777:Anesthetics; D000900:Anti-Bacterial Agents; D065607:Cytochrome P-450 Enzyme Inhibitors; D013565:Sympatholytics; D014991:Xylazine; D015016:Yohimbine; D002701:Chloramphenicol