Prolonged persistence on the ocular surface of fortified gentamicin ointment as compared to fortified gentamicin eye drops.

Purpose: A comparative study on the elimination of gentamicin from the ocular surface and the concentration of gentamicin in the anterior chamber following application of either an ointment or eye drops containing equal concentrations (1.5%) of gentamicin.
Methods: A disc-diffusion test was used to determine the concentration of gentamicin in fornix inferior of 10 persons. The anterior chamber concentration of gentamicin was determined in 5 cataract patients by the TDX analyzer, Abbot Laboratories, II., USA.
Results: Ten minutes following application, the concentration of gentamicin was significantly higher in the eyes receiving ointment (310.6 mg/L) compared to drops (45 mg/L) (p<0.01). Furthermore, gentamicin could be detected 40 minutes after application in the eyes receiving ointment compared to 10 minutes in the eyes receiving drops. The anterior chamber concentration of gentamicin after application of either drops or ointment was lower than 0.6 mg/L and thus below detection limit.
Conclusions: The persistence of gentamicin ointment was significantly longer on the ocular surface as compared to gentamicin eye drops. Gentamycin ointment may thus provide a means to reduce the high application frequency presently in use with eye drops to treat bacterial keratitis and thereby reduce patient inconvenience, especially during nighttime.