Sedative effects of medetomidine and its reversal by atipamezole in llamas

Abstract

Objective - To determine a dose of medetomidine that will induce sedation in llamas, to assess effects of medetomidine sedation on arterial blood gas variables, and to determine efficacy of atipamezole in reversing medetomidine-induced sedation. Design - Prospective, randomized clinical trial. Animals - 15 clinically normal adult llamas. Procedure - 9 llamas received various doses of medetomidine (0.01, 0.02, or 0.03 mg/kg [0.005, 0.009, or 0.014 mg/lb] of body weight, IM). Heart and respiratory rates and sedative effects were recorded. Using the lowest dose that induced deep sedation, 6 different llamas were used to assess effects of medetomidine on arterial blood gas variables. These same 6 llamas were later given atipamezole (0.125 mg/kg [0.057 mg/lbj, IV) 30 minutes after medetomidine injection. Heart and respiratory rates, sedative effects, and time from atipamezole injection to standing were recorded. Results - Sedation began 6.67 ± 1.15 minutes (mean ± SD) after medetomidine administration (0.03 mg/kg, IM). Arterial blood gas variables measured 30 and 60 minutes after injection were not different from baseline. Llamas that did not receive atipamezole remained recumbent for 91.50 ± 24.68 minutes. After atipamezole administration, llamas were able to stand in 5.80 ± 3.27 minutes. Clinical implications - Medetomidine induced light to deep sedation in a dose- dependent manner in clinically normal llamas. A dose of 0.03 mg/kg induced deep sedation with a short period of analgesia. Atipamezole rapidly reversed effects of medetomidine, and llamas recovered quickly and were soon able to stand.