The Early Ophthalmic Effects of Vatinoxan in Healthy Detomidine-Sedated Horses.

OBJECTIVE

To evaluate the short-term ophthalmic effects of vatinoxan, a peripherally selective alpha2-adrenoceptor antagonist, in detomidine-sedated horses.

ANIMALS STUDIED: Seven healthy horses without ophthalmic disease in a randomized, masked, two-period crossover study design, with a ≥ 7-day rest period.

PROCEDURES: After a bilateral palpebral block (lidocaine 40 mg) and baseline data collection, horses received intravenous detomidine (20 μg/kg [DET]) or DET with vatinoxan (200 μg/kg [DET-VAT]). Intraocular pressure (IOP) was measured from the left eye while tear production (Schirmer tear test -1; STT) and vertical pupil diameter (VPD) were measured from the right eye at pre-determined intervals until 25 min post-treatment. Comparisons within and between treatments were analyzed with Student's t-tests (for IOP and VPD) or Wilcoxon's Rank Sum tests (for STT) followed by the Holm-Bonferroni post hoc adjustment.

RESULTS

The overall post-treatment IOP across time points was lower after DET (15.7 ± 1.9 [mean ± standard deviation] mmHg) than DET-VAT (16.9 ± 2.0 mmHg) (p = 0.01). IOP remained significantly (p < 0.05) lower than baseline after DET for the whole 25 min observational period, while for DET-VAT the corrected pairwise comparisons to baseline did not reach significance. The median (range) STT increased from baseline 17 (13-25) mm/min to 24 (18-35) mm/min (p = 0.022) at 25 min after DET and from 18 (11-35) mm/min to 30 (18-35) mm/min (p = 0.022) after DET-VAT, respectively. VPD did not differ significantly from baseline after either treatment.

CONCLUSIONS

Vatinoxan alleviated detomidine-associated early decrease in IOP in healthy horses.