title: Cardiopulmonary effects of combinations of medetomidine hydrochloride and atropine sulphate in dogs.
abstract: Medetomidine and xylazine are alpha 2 adrenoceptor agonists which are used as sedatives and premedicants in small animals. However, bradycardia is a side effect and the use of atropine sulphate has been recommended to counteract it. This study investigated the effects of combining medetomidine (40 micrograms/kg) and atropine (30 micrograms/kg) on the cardiopulmonary function of six dogs. Medetomidine administered alone caused severe bradycardia, but hypertension was mild and transient. Medetomidine and atropine administered together caused an initial bradycardia, but within 15 minutes there was tachycardia accompanied by a mean arterial blood pressure of 210 mm Hg. When atropine was administered 30 minutes before medetomidine, tachycardia and hypertension were observed within five minutes of the medetomidine injection. Thus, although atropine will counteract medetomidine-induced bradycardia, its use results in prolonged and severe hypertension, in association with the tachycardia. Although atropine may be life-saving when bradycardia is profound, its indiscriminate use in combination with alpha 2 adrenoceptor agonists may be disadvantageous.
authors.affiliation: Department of Large Animal Medicine and Surgery, Royal Veterinary College, Hatfield, Hertfordshire.
authors.forename: H I
authors.initials: HI
authors.lastname: Alibhai
authors.forename: K W
authors.initials: KW
authors.lastname: Clarke
authors.forename: Y H
authors.initials: YH
authors.lastname: Lee
authors.forename: J
authors.initials: J
authors.lastname: Thompson
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D001919:Bradycardia / Q000139:chemically induced / Q000188:drug therapy / Q000662:veterinary; D004283:Dog Diseases / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology; D004285:Dogs; D004338:Drug Combinations; D004347:Drug Interactions; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006973:Hypertension / Q000503:physiopathology / Q000662:veterinary; D007093:Imidazoles / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D007273:Injections, Intramuscular; D008297:Male; D020926:Medetomidine; D012143:Respiratory Physiological Phenomena; D012137:Respiratory System / Q000187:drug effects*
chemical_list: D000316:Adrenergic alpha-Agonists; D000889:Anti-Arrhythmia Agents; D004338:Drug Combinations; D007093:Imidazoles; D001285:Atropine; D020926:Medetomidine