Measurement of plasma gentamicin concentrations postchemical ciliary body ablation in dogs with chronic glaucoma

Objective To investigate the absorption of gentamicin into the plasma after an intravitreal injection in dogs and to report the success rate of this procedure in lowering the intraocular pressure. Animals Twenty‐four client‐owned dogs with chronic, end‐stage glaucoma. Procedures Dogs received a unilateral (22) or bilateral (2) intravitreal injection of 25–40 mg of gentamicin (mean ± SD dose 2.57 ± 1.65 mg/kg and range 0.61–7.50 mg/kg) and 1 mg of dexamethasone per eye. Blood samples were collected at various time points following the intravitreal injection. Plasma concentrations of gentamicin were determined by liquid chromatography and mass spectrometry. Results The total plasma concentration of gentamicin ranged from 0.21 to 9.71 μg/mL (mean ± SD 2.15 ± 2.03). The mean gentamicin CMAX was 2.29 μg/mL at 2.54 h with a terminal half‐life of 9.8 h. The success rate of the chemical ablation procedure was 86.4% (19/22 eyes) in dogs that had at least 1 month of follow‐up. Conclusions Intravitreal injection of gentamicin in eyes with chronic glaucoma resulted in detectable plasma levels in dogs and was successful in lowering the intraocular pressure in 86.4% of the eyes after the first procedure.