CARDIOPULMONARY EFFECTS OF COMBINATIONS OF MEDETOMIDINE HYDROCHLORIDEAND ATROPINE SULFATE IN DOGS

Medetomidine and xylazine are alpha 2 adrenoceptor agonists which are used as sedatives and premedicants in small animals, However, bradycar dia is a side effect and the use of atropine sulphate has been recomme nded to counteract it. This study investigated the effects of combinin g medetomidine (40 mu g/kg) and atropine (30 mu g/kg) on the cardiopul monary function of six dogs. Medetomidine administered alone caused se vere bradycardia, but hypertension was mild and transient, Medetomidin e and atropine administered together caused an initial bradycardia, bu t within 15 minutes there was tachycardia accompanied by a mean arteri al blood pressure of 210 mm Hg. When atropine was administered 30 minu tes before medetomidine, tachycardia and hypertension were observed wi thin five minutes of the medetomidine injection, Thus, although atropi ne will counteract medetomidine-induced bradycardia, its use results i n prolonged and severe hypertension, in association with the tachycard ia, Although atropine may be life-saving when bradycardia is profound, its indiscriminate use in combination with alpha 2 adrenoceptor agoni sts may be disadvantageous.