General purpose antimicrobial ophthalmic solutions evaluated using new pharmacokinetic parameter of maximum drug concentration in aqueous.

PURPOSE In order to determine whether the one-component method for calculating drug concentration in the aqueous (AQC(max)) is useful for selecting an appropriate ophthalmic solution, six general purpose antimicrobial ophthalmic solutions already on the market were investigated. METHODS The drugs examined were levofloxacin (LVFX), chloramphenicol (CP), erythromycin lactobionate (EM), micronomicin sulfate (MCR), cefmenoxime hydrochloride (CMX), and disodium sulfobenzyl penicillin (SBPC). Fifty microliters of each solution was instilled into the cul-de-sac of New Zealand White rabbit eyes three times at 15-minute intervals. The drug concentrations in the aqueous humor 10, 30, 60, 120, and 240 minutes after the final instillation were examined by high performance liquid chromatography (HPLC) and/or bioassay. The AQC(max) was calculated using the one-compartment method. RESULTS The calculated AQC(max) was 2.5 microg/mL (HPLC method) and 2.28 microg/mL (bioassay method) for LVFX, 2.17 microg/mL for CP, and 0.45 microg/mL for EM. The AQC(max) for CMX, MCR, and SBPC could not be calculated by the one-compartment method. CONCLUSIONS The AQC(max) of LVFX was higher than that of the two other general purpose antimicrobial ophthalmic solutions. The AQC(max) of these drugs might be a useful parameter for selecting an appropriate ophthalmic solution for the treatment of infected eyes.