Comparison of intranasal atipamezole by atomization or drops with intramuscular injection for reversing sedative effects of medetomidine in healthy dogs.

Objective: To determine and compare the efficacy of intranasal (IN) atomization, IN drops, and IM injection of atipamezole for reversal of medetomidine-induced sedation in healthy dogs.

Design: Prospective, randomized, blinded study.

Setting: University teaching hospital.

Animals: Forty mixed-breed, shelter-owned dogs with an average weight of 29.9 ± 5.6 kg (mean ± SD) that required sedation for minor diagnostic or therapeutic procedures.

Interventions: Atipamezole was administered by a dog handler at 200 µg/kg via IN atomization (ATI-IN_A, n = 10), IN drops (ATI-IN_D, n = 10), or IM injection (ATI-IM, n = 10) 20 minutes following medetomidine administration (40 µg/kg). A control group (n = 10) received no atipamezole.

Measurements and main results: Ease of atipamezole administration was evaluated. Sedation score, heart rate (HR), respiratory rate (RR), and blood pressure (BP) were recorded pre-medetomidine administration (T0), pre-atipamezole administration (T20), and at multiple intervals following atipamezole administration. ATI-IM resulted in the fastest recovery, followed by ATI-IN_A, with ATI-IN_D being the slowest. The adverse cardiovascular impacts of medetomidine were not completely mitigated. ATI-IM showed initial HR restoration followed by a decline. HR in both IN groups showed a slower increase compared to ATI-IM, but no subsequent decline was observed. ATI-IM resulted in a transient decrease in BP, though dogs remained normotensive. A gradual reduction in BP was noted in the IN groups. At T50, RR of all atipamezole groups differed from control, and a significant increase in RR was observed in ATI-IM dogs compared to pre-atipamezole value. No adverse effects were observed.

Conclusions: All routes for atipamezole administration effectively reversed medetomidine-induced sedation, with ATI-IM being fastest. IN routes were easy for the dog handler to administer, making them viable alternatives in cases of accidental drug exposure, particularly outside a hospital setting.