Effect of vatinoxan co-administered with medetomidine on intraocular pressure and pupil diameter in healthy dogs

Medetomidine, an alpha-2 adrenoreceptor agonist, is used for sedation. This study aimed to determine the influence of the alpha-2 adrenoreceptor antagonist vatinoxan, co-administered with medetomidine, on healthy dogs' intraocular pressure (IOP) and pupil diameter (PD). A prospective, randomised, masked clinical study was performed. A total of 40 conscious dogs were allocated to one of two groups: medetomidine 0.01 mg/kg with vatinoxan 0.2 mg/kg intravenously (MV-group, <i>n = </i>20) or medetomidine 0.01 mg/kg intravenously (M-group, <i>n</i> = 20). The IOP, PD, heart rate, and mean arterial pressure were measured prior to baseline and 5, 10, and 20 min after drug administration. Data were analysed using one- and two-way repeated measures ANOVA or their non-parametric equivalents (<i>P</i> < 0.05). No significant differences in IOP within or between groups were recorded. In the MV-group, PD remained unchanged compared to baseline. In the M-group, PD significantly (<i>P</i> = 0.007, <i>P</i> < 0.001, <i>P</i> < 0.001) decreased compared to baseline at all observation times. PD was significantly (<i>P</i> = 0.010, <i>P</i> < 0.001, <i>P</i> < 0.001) smaller in the M-group at all observation times compared to the MV-group. Vatinoxan co-administered with medetomidine, as well as medetomidine alone, did not significantly influence IOP. Vatinoxan with medetomidine did not affect PD, while medetomidine alone significantly reduced it.