Transscleral and Transcorneal Iontophoresis of Vancomycin in Rabbit Eyes

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Abstract
We examined the ability of transscleral and transcorneal iontophoresis to deliver vancomycin into the aqueous humor, the vitreous humor, and the cornea of rabbit eyes. Control eyes receiving subconjunctival injection (25 mg) attained peak aqueous, vitreous, and corneal concentrations (mean ± S.E.M.) of 14.73±0.35 mcg/ml (at 4 hours after injection), 1.10±0.78 mcg/ml (2 hours), and 1167±63 mcg/g (1 hour), respectively. Eyes receiving transscleral iontophoresis (3.5 mA for 10 minutes) attained significantly higher vitreal levels than controls: 6.33±0.25 mcg/ml (p<0.001; 1 hour), 13.43±2.32 mcg/ml (p<0.01; 2 hours), 11.93±0.76 mcg/ml (p<0.001; 4 hours), 8.40±0.60 mcg/ml (p<0.001; 8 hours). Eyes receiving transcorneal iontophoresis (0.5 mA for 5 minutes) attained earlier and significantly higher aqueous and corneal levels than controls. Aqueous humor levels were 16.20±3.19 mcg/ml (p<0.05; 1 hour) and 20.20±0.43 mcg/ml (p<0.001; 2 hours). Corneal levels were 10799±755 mcg/g (p<0.001; 0.5 hour), 4856±606 mcg/g (p<0.005; 1.0 hour), 2185±71 mcg/g (p<0.001; 2 hours), and 710±112 mcg/g (p<0.025; 4 hours). Corneal endothelial cell counts were decreased by 8.8% (p=0.08) after transcorneal iontophoresis of vancomycin and 5.4% (p<0.02) following Balanced Salt Solution (BSS). However, corneal thickness were not significantly increased by iontophoresis of either vancomycin or BSS. These experiments show that transscleral and transcorneal iontophoresis are efficacious in delivering high concentrations of vancomycin into the aqueous and vitreous humor and the cornea.