The clinical effectiveness of atipamezole as a medetomidine antagonist in the dog.
The efficacy of atipamezole, a recently introduced alpha 2-adrenoceptor antagonist, in reversing medetomidine-induced effects in dogs was investigated in a clinical study. Dogs from eight Finnish small-animal hospitals were sedated with a 40-microgram/kg dose of the alpha 2-agonist medetomidine i.m. In the first part of the study (n = 319), a randomized, double-blind design with respect to the dose of atipamezole (0, 80, 160 and 240 micrograms/kg i.m.) was used. In a separate study (n = 358), which was an open trial, the selected dose of atipamezole was 200 micrograms/kg i.m. Atipamezole at dose rates of 80-240 micrograms/kg rapidly and effectively reversed medetomidine-induced deep sedation-analgesia, recumbency and bradycardia. The median arousal time after atipamezole was 3-5 min, and walking time was 6-10 min compared to greater than 30 min for both effects after placebo. Heart rate also increased in a dose-related manner after atipamezole administration. The investigators' overall evaluation of the ability of atipamezole to reverse the effects of medetomidine was 'good' in 90%, and 'moderate' in 9% of cases. Relapse into sedation was reported in three individual cases. Side-effects were minimal. It is concluded that at doses four- to sixfold the medetomidine dose, atipamezole is a highly effective and safe agent in reversing medetomidine-induced sedation-analgesia, recumbency and bradycardia in dogs in veterinary practice.
Vähä-Vahe
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Farmos Group Ltd., Research Center, Turku, Finland.
D000317:Adrenergic alpha-Antagonists / Q000009:adverse effects / Q000494:pharmacology*; D000700:Analgesics / Q000037:antagonists & inhibitors; D000818:Animals; D002986:Clinical Trials as Topic; D004285:Dogs / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000037:antagonists & inhibitors*; D007093:Imidazoles / Q000009:adverse effects / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D008297:Male; D020926:Medetomidine; D016032:Randomized Controlled Trials as Topic; D014839:Vomiting / Q000139:chemically induced
D000317:Adrenergic alpha-Antagonists; D000700:Analgesics; D006993:Hypnotics and Sedatives; D007093:Imidazoles; C050701:atipamezole; D020926:Medetomidine