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Plasma gentamicin concentrations in dogs following postchemical ciliary body ablation
A D V A N C E S
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Plasma Gentamicin Concentrations in Dogs Following Postchemical Ciliary Body Ablation Background Pharmacologic destruction of the ciliary body can be accomplished by an intravitreal injection of a combination of gentamicin and dexamethasone to reduce the intraocular pressure (IOP) for the treatment of chronic glaucoma in dogs. The mechanism by which gentamicin causes destruction of the ciliary body epithelium is not understood. Reported complications of ciliary body ablation with intravitreal gentamicin in dogs include intraocular inflammation, corneal opacity, cataract formation, intraocular hemorrhage, and phthisis bulbi. Gentamicin is an aminoglycoside antibiotic that may impair renal function and has both vestibulotoxic and ototoxic effects. Due to the severity of the side effects of gentamicin, the goal of this study was to assess the potential for systemic absorption of gentamicin after intraocular administration in dogs.
Objectives To investigate the absorption of genta micin into the plasma after an intravitreal injection in dogs and to report the success rate of this procedure in lowering the IOP.
Procedure Dogs diagnosed with chronic, end-stage glaucoma after complete ophthalmic examination were eligible for this study. Chronic glaucoma was defined as IOP equal or greater than 25 mg Hg as well as other clinic deficiencies. Dogs received a unilateral or bilateral intravitreal injection of gentamicin and 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.
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A D V A N C E S
Results A total of 26 eyes in 24 dogs were included in the study. The population consisted of a variety of breeds, ages, and sexes. The total plasma concentration of gentamicin ranged from 0.21 to 9.71 ug/mL. The mean gentamicin maximum concentration was 2.29 ug/mL at 2.54 hours with a terminal half-life of 9.8 hours. The success rate of the chemical ablation procedure was 86.4% in dogs that had at least one month of follow-up.
Author 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. Caution should be exercised when administering an intravitreal injection of gentamicin to a smaller patient or in patients with renal impairment.
Inclusions One figure, 2 tables, 19 references.
Editor annotation Intravitreal injection of gentamicin has been utilized as a cost-effective method to control chronic, blinding glaucoma in dogs since the early 1980s. The generally accepted dose of intravitreal gentamicin is 25 mg with or without the addition of 1 mg of dexamethasone. In multiple studies, the efficacy of this procedure in controlling IOP is about 85%. For many years, there has not been any objective data regarding the systemic absorption of gentamicin when it is injected intravitreally in dogs. The general recommendation has been to not exceed the maximum daily dose (4.4 mg/kg) of gentamicin, particularly in small dogs. This study of plasma gentamicin levels, as well as another recent study of serum gentamicin levels, both document that there is little to no gentamicin in the systemic circulation 24 hours after intravitreal injection. I have been utilizing this procedure for the past 23 years with good success. With the exception of very small dogs, I use 25 mg of gentamicin without any dexamethasone. In small dogs, I reduce the dose to not exceed the maximum daily dose of gentamicin. In patients with pre-existing renal disease, it is my recommendation to not utilize this procedure and consider an enucleation or intrascleral prosthesis. (RH)
Rankin AJ, Lanuza R, et. al. Measurement of plasma gentamicin concentrations postchemical ciliary body ablation in dogs with chronic glaucoma. Vet Ophthalmol 2016;19:57-62
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Plasma Gentamicin Concentrations in Dogs Following Postchemical Ciliary Body Ablation Background Pharmacologic destruction of the ciliary body can be accomplished by an intravitreal injection of a combination of gentamicin and dexamethasone to reduce the intraocular pressure (IOP) for the treatment of chronic glaucoma in dogs. The mechanism by which gentamicin causes destruction of the ciliary body epithelium is not understood. Reported complications of ciliary body ablation with intravitreal gentamicin in dogs include intraocular inflammation, corneal opacity, cataract formation, intraocular hemorrhage, and phthisis bulbi. Gentamicin is an aminoglycoside antibiotic that may impair renal function and has both vestibulotoxic and ototoxic effects. Due to the severity of the side effects of gentamicin, the goal of this study was to assess the potential for systemic absorption of gentamicin after intraocular administration in dogs.
Objectives To investigate the absorption of genta micin into the plasma after an intravitreal injection in dogs and to report the success rate of this procedure in lowering the IOP.
Procedure Dogs diagnosed with chronic, end-stage glaucoma after complete ophthalmic examination were eligible for this study. Chronic glaucoma was defined as IOP equal or greater than 25 mg Hg as well as other clinic deficiencies. Dogs received a unilateral or bilateral intravitreal injection of gentamicin and 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.
Page 6
A D V A N C E S
Results A total of 26 eyes in 24 dogs were included in the study. The population consisted of a variety of breeds, ages, and sexes. The total plasma concentration of gentamicin ranged from 0.21 to 9.71 ug/mL. The mean gentamicin maximum concentration was 2.29 ug/mL at 2.54 hours with a terminal half-life of 9.8 hours. The success rate of the chemical ablation procedure was 86.4% in dogs that had at least one month of follow-up.
Author 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. Caution should be exercised when administering an intravitreal injection of gentamicin to a smaller patient or in patients with renal impairment.
Inclusions One figure, 2 tables, 19 references.
Editor annotation Intravitreal injection of gentamicin has been utilized as a cost-effective method to control chronic, blinding glaucoma in dogs since the early 1980s. The generally accepted dose of intravitreal gentamicin is 25 mg with or without the addition of 1 mg of dexamethasone. In multiple studies, the efficacy of this procedure in controlling IOP is about 85%. For many years, there has not been any objective data regarding the systemic absorption of gentamicin when it is injected intravitreally in dogs. The general recommendation has been to not exceed the maximum daily dose (4.4 mg/kg) of gentamicin, particularly in small dogs. This study of plasma gentamicin levels, as well as another recent study of serum gentamicin levels, both document that there is little to no gentamicin in the systemic circulation 24 hours after intravitreal injection. I have been utilizing this procedure for the past 23 years with good success. With the exception of very small dogs, I use 25 mg of gentamicin without any dexamethasone. In small dogs, I reduce the dose to not exceed the maximum daily dose of gentamicin. In patients with pre-existing renal disease, it is my recommendation to not utilize this procedure and consider an enucleation or intrascleral prosthesis. (RH)
Rankin AJ, Lanuza R, et. al. Measurement of plasma gentamicin concentrations postchemical ciliary body ablation in dogs with chronic glaucoma. Vet Ophthalmol 2016;19:57-62