Residence Time of Netilmicin in Tears

PURPOSE.To determine the concentration of netilmicin in tears after eye drop administration. METHODS.A clinical study was carried out on 32 healthy volunteers. Subjects were divided into four groups and underwent tear collection at 5, 10, 20, and 60-minutes after drug administration, respectively. Tear samples were collected through capillary suction from the inferior conjunctival “cul-de-sac” and analyzed by high-pressure liquid chromatography (HPLC). RESULTS.Netilmicin concentration in tears decreased after a first order kinetics, a best-fit curve was drawn and the minimum inhibitory concentration (MIC 90 ) intersection for the most common ocular pathogens was calculated. CONCLUSIONS.The extrapolation of the curve shows that the concentration of netilmicin on the ocular surface can be effective against microorganisms more than 120 minutes after eye drop instillation.