Animal experiment:

Dogs[1]Eight dogs receive either dexmedetomidine (10 μg/kg), Vatinoxan (250 μg/kg or dexmedetomidine (10 μg/kg) with increasing doses of Vatinoxan (250 μg/kg, 500 μg/kg and 750 μg/kg). Treatments are given intravenously (i.v.) in a randomized, crossover design with a 14-day ishout period. Systemic hemodynamics and arterial blood gas analyses are recorded at baseline and at intervals up to 90 min after drugs administration[1].Cats[2]Cats are administered seven IV treatments are administered at least 2 weeks apart, consisting of dexmedetomidine 12.5 μg/kg (D12.5) and 25 μg/kg (D25), Vatinoxan 300 μg/kg (M300), and D25 combined with 75, 150, 300 and 600 μg/kg of Vatinoxan (D25M 75, D25M150, D25M300 and D25M600, respectively). Heart rates (HR) are recorded via telemetry and sedation assessed with a simple descriptive score and a visual analogue scale prior to treatments and at intervals until 8 hours thereafter[2].

Vatinoxan hydrochloride (MK-467 hydrochloride;L-659066 hydrochloride) is a peripheral α2 adrenergic receptor antagonist.

Vatinoxan alone increases cardiac index and tissue oxygen delivery and has no deleterious adverse effects. Vatinoxan attenuates or prevents dexmedetomidine’s systemic hemodynamic effects in a dose-dependent manner when given simultaneously i.v. but has no effect on the pulmonary outcome in conscious dogs. A 50:1 dose ratio (Vatinoxan:dexmedetomidine) induces the least alterations in cardiovascular function[1]. Vatinoxan dose-dependently attenuates the bradycardia associated with dexmedetomidine, and shortens the sedative effect without altering its quality. Vatinoxan may be useful in attenuating reductions in heart rate in conscious catsadministered dexmedetomidine[2].

[1]. Honkavaara JM, et al. The effects of increasing doses of MK-467, a peripheral alpha(2)-adrenergic receptor antagonist, on the cardiopulmonary effects of intravenous dexmedetomidine in conscious dogs. J Vet Pharmacol Ther. 2011 Aug;34(4):332-7. [2]. Honkavaara J, et al. The effect of MK-467, a peripheral α2-adrenoceptor antagonist, on dexmedetomidine-inducedsedation and bradycardia after intravenous administration in conscious cats. Vet Anaesth Analg. 2017 Feb 22. pii: S1467-2987(16)31387-3.