Penetration of Chlorhexidine into the Rabbit Anterior Chamber Following Topical Administration

Abstract

Abstract: : Purpose:To evaluate corneal and anterior chamber penetration and corneal toxicity following topical chlorhexidine in a rabbit model Methods: 20% chlorhexidine digluconate stock solution was diluted in saline and 0.5% ethyl alcohol to prepare three concentrations: 0.02% (Group A), 0.1% (Group B) and 0.2% (Group C). A vehicle control was also prepared (Group D/N=8). Saline only was used for scanning electron microscopy studies (Group E/N=2). For groups A-C, (N=48 eye total) one drop of chlorhexidine solution was applied to both normal and abraded corneas every 10 minutes for a total of 10 doses. Abrasions were created first using a 7.5 mm diameter Weck trephine to score the cornea. A #15 Beaver blade was then used to remove the corneal epithelium. 150 ul of aqueous fluid were removed from the anterior chamber using a 25g needle on a tuberculin syringe. Corneal tissue was also harvested using a 9.0 mm trephine and corneal scissors and then homogenized for chlorhexidine determination. Chlorhexidine concentrations were determined by HPLC. Scanning electron microscopic evaluation was performed on the epithelium and endothelium of corneas from Groups A-C (N=2/group)and Group E. Statistical analysis was performed using one-way ANOVA Results: The mean corneal chlorhexidine concentration was 0.28 µg/mg ± 0.14, 0.105 ± 0.105µg/mg and 0.575 ± 0.072 µg/mg respectively in Groups A, B, and C in the normal corneas and 1.95 ± 0.59 µg/mg, 1.01±0.357 µg/mg and 0.22 ± 0.063 µg/mg respectively in the abraded corneas. Debrided groups had higher levels of chlorhexadine concentration across all groups. Differences in chlorhexidine concentrations in all three debrided corneal groups and in the two higher concentration normal cornea groups were found to be statistically significant. Aqueous humor chlorhexidine concentrations were present in some groups but no statistical difference was found between control and treated groups in both normal and debrided corneas. When using scanning electron microscopy to compare with saline control, epithelial and endothelial toxicity progressively worsened as chlorhexidine concentrations increased. In the 0.2% group there was significant epithelial microvilli loss as well as endothelial polymorphism and polymegathism. Conclusions: Topically applied chlorhexidine can penetrate across the intact cornea. Removing the corneal epithelium increases the penetration. Higher doses of chlorhexidine results in increased penetration. Toxicity appears to be dose related.

Keywords: drug toxicity/drug effects • cornea: basic science • cornea: epithelium