[Amphotericin B--bioavailability in the cornea. Studies with local administration of liposome incorporated...

Amphotericin B remains an important antifungal agent in the treatment of ocular mycosis. Since topical ocular application is limited because of ocular irritation and poor penetration, we studied the pharmacokinetics of amphotericin B encapsulated in unilamellar liposomes (AmBisome). One drop (20 microliters) of AmBisome or an equivalent concentration of amphotericin B was applied to rabbit eyes. Drug concentrations were measured 15, 60, 120 and 240 min following administration of the agents by HPLC in cornea and aqueous humor. The effect of intact (group A) and debrided corneal epithelium (group B) was also studied. Corneal amphotericin B levels were significantly higher (P < 0.01) after 15 min in animals receiving amphotericin B as compared to AmBisome in group A. At later time points no differences in the corneal drug levels were found, and the drug levels following AmBisome application were remarkably stable. Epithelial removal resulted in increased corneal drug levels following application of both amphotericin B preparations. Significantly higher drug levels were observed after free amphotericin B treatment at 15-60 min (P < 0.01). Drug levels in the aqueous humor did not differ between the two amphotericin B preparations and remained below therapeutically effective concentrations. These results suggest that topically delivered AmBisome provides stable corneal drug levels, but has the potential benefit of lowered ocular toxicity.