Effects of intravenous detomidine on Schirmer tear test results in clinically normal horses

Abstract This study was conducted to determine the effects of intravenous detomidine on schirmer tear test (STT) results in clinically normal horses . Eighteen adult horses were randomly divided into two groups of nine horses each. The treatment group was sedated with intravenous detomidine alone (20 μg/kg) and the control group received only intravenous saline (0.2 ml/100 kg). STT was performed just before intravenous administration of detomidine or saline in treatment and control groups respectively. STTs were repeated 5, 20, 60 and 120 mins later. Horses enrolled in this study consisted of nine males and nine females. Breeds were Arabian and Hanoverian, ranging from 3 to 6 years in age. In the treatment group, the pretreatment and subsequent post-treatment mean ± SD values were 17.0 ± 6.9 (0 min), 11.8 ± 2.9 (5 min), 12.1 ± 2.0 (20 min), 12.1 ± 3.1 (60 min), and 15.0 ± 2.8 (120 min) mm wetting/minute. In this group of horses, a significant reduction was observed in STT values at 5, 20 and 60 min after treatment with detomidine hydrochloride in comparison to the pretreatment values (ANOVA with post hoc testing; P 5 =0.004, P 20 =0.007, P 60 = 0.006). There was no significant difference between baseline values and post-treatment values in the control saline group (P ≥ 0.08). We conclude that intravenous detomidine causes a significant reduction in STT values in clinically normal horses. In horses, practitioners should measure STT values prior to intravenous administration of detomidine in order to accurately assess the results.