Effect of sedation with xylazine and ketamine on intraocular pressure in New Zealand white rabbits

To determine the effects of intravenous and intramuscular xylazine-ketamine on intraocular pressure (IOP) in laboratory rabbits, 10 New Zealand white rabbits received xylazine (0.46 mg/kg) and ketamine (1.5 mg/kg) intravenously whereas another 10 rabbits received intramuscular xylazine (10 mg/kg) and ketamine (50 mg/kg). IOP was measured at baseline and 5, 10, 20, and 25 min after administration in rabbits that were injected intravenously and at baseline and 10, 20, 30, and 45 min in rabbits injected intramuscularly. Baseline IOP (mean ± 1 SD; intravenous group, 20.15 ± 2.24 mm Hg; intramuscular group, 19.03 ± 1.77 mm Hg) did not differ between groups. Compared with baseline values, IOP decreased significantly after intravenous administration at 10, 20, and 25 min (decreases of 2.73, 4.10, and 4.55 mm Hg, respectively) but not at 5 min (decrease of 1.40 mm Hg). IOP in intramuscularly dosed rabbits showed significant differences from baseline at 10, 20, 30, and 45 min (decreases of 2.88, 3.30, 3.95, and 4.60 mm Hg, respectively). In the intravenous group, IOP differed at 10 min compared with 25 min (1.83 mm Hg, P = 0.0143) but not at 20 min compared with 25 min (0.450 mm Hg). In the intramuscular group, differences in IOP at 10 min compared with 20 min, 20 min compared with 30 min, and 30 min compared with 45 min were nonsignificant. Intravenous and intramuscular xylazine-ketamine decreased IOP in laboratory rabbits and may be used safely during ocular procedures for which increased IOP is a concern.