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 ocul ar surface and the concentration of gentamicin in the anterior chamber foll owing application of either an ointment or eye drops containing equal conce ntrations (1.5%) of gentamicin. Methods: A disc-diffusion test was used to determine the concentration of g entamicin in fornix inferior of 10 persons. The anterior chamber concentrat ion 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) compa red to drops (45 mg/L) (p<0.01), Furthermore, gentamicin could be detected 40 minutes after application in t he eyes receiving ointment compared to 10 minutes in the eyes receiving dro ps. The anterior chamber concentration of gentamicin after application of e ither drops or ointment was lower than 0.6 mg/L and thus below detection li mit. Conclusions: The persistance of gentamicin ointment was significantly longe r on the ocular surface as compared to gentamicin eye drops. Gentamycin oin tment may thus provide a means to reduce the high application frequency pre sently in use with eye drops to treat bacterial keratitis and thereby reduc e patient inconvenience, especially during nighttime.