The effect of intramuscular atipamezole on head height and sedation scores in detomidine-sedated horses.

Objective: To assess the effect of two different doses of intramuscular atipamezole on head height (HH) in horses after sedation with detomidine.

Study design: Randomized, blinded, triple crossover study.

Animals: Eight healthy adult horses.

Methods: Baseline HH was measured before detomidine (40 μg kg^-1) was injected intravenously. HH was measured at 10 and 20 minutes after injection. Then, saline, atipamezole 60 μg kg^-1 (AT60) or 120 μg kg^-1 (AT120) was injected intramuscularly. HH measurements were repeated at 10 minutes intervals for 100 minutes. HH data were analyzed with a linear mixed model. Significance was set at p < 0.05. Data are reported as mean ± standard deviation.

Results: Baseline HH (cm) was 118 ± 14 for saline, 120 ± 10 for AT60, and 115 ± 14 for AT120 and was not significantly different among groups (p > 0.05). AT60 HH was greater than saline at 80 (33 ± 11 versus 28 ± 11), 90 (45 ± 15 versus 26 ± 13), and 110 (57 ± 24 versus 32 ± 11) minutes (all p < 0.002). AT120 HH was greater than saline at 50 (33 ± 16 versus 22 ± 8), 80 (44 ± 11 versus 28 ± 11), 90 (45 ± 11 versus 26 ± 13), 100 (52 ± 18 versus 30 ± 16) and 110 (64 ± 23 versus 32 ± 11) minutes (all p < 0.002). HH was not significantly different at any time between AT60 and AT120 (all p > 0.05).

Conclusions and clinical relevance: Horses administered atipamezole showed signs of reversal of sedation, as evaluated by HH compared with saline. Horses administered the higher dose of atipamezole had HH greater than saline sooner than horses administered the lower dose. Intramuscular atipamezole may be useful for reversal of detomidine sedation in horses.