Ganciclovir ophthalmic gel in herpes simplex virus rabbit keratitis: intraocular penetration and efficacy

A chronic administration of three ganciclovir gels (0.2%, 0.05%, 0.0125%) was compared with a placebo gel and a 3% acyclovir ophthalmic ointment in the treatment of HSV-1 rabbit keratitis. All the ganciclovir gels showed a clinical efficacy: a significant reduction of the corneal ulcer area, clouding and vascularization (p < 0.05) and a fast inhibition of HSV isolates into tear film with the 0.2% and 0.05% ganciclovir gels. However the efficacy was slower than using acyclovir ointment. No significant difference could be shown between the 0.2% and 0.05% ganciclovir gels or the 0.05% ganciclovir gel and the acyclovir treatment on viral isolation, when it was performed on pooled samples. The distribution of ganciclovir and acyclovir into the rabbit eyes (HPLC methods), were similar but markedly higher in solid tissues than ocular fluids. It might explain the recovery from tissue damages. The mean corneal ganciclovir concentrations were largely higher than ED 50 of ganciclovir for HSV-1. No toxicity was expected, due to very limited systemic availability. This study suggests a comparable activity on HSV-1 superficial keratitis between 0.05%, 0.2% ganciclovir gels and 3% acyclovir ointment. Higher concentration of ganciclovir gels are probably necessary in order to treat the HSV-1 kerato-uveitis.