Concentration of Latanoprost Ophthalmic Solution after 4 to 6 Weeks’ Use in an Eye Clinic Setting

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To determine the concentration of latanoprost in bottles of latanoprost ophthalmic solution 0.005% after 4 or 6 weeks of use in patients in an eye clinic setting. Patients treated with latanoprost for open-angle glaucoma or ocular hypertension were randomly assigned to refill their prescriptions either at the Doheny Eye Institute clinic or a local pharmacy. Patients who used latanoprost binocularly were asked to return bottles to the clinic after 4 weeks of use and nonrefrigerated storage, and those who used latanoprost monocularly were asked to return used bottles after 6 weeks. Patients were then interviewed to determine bottle storage information and doses missed. Latanoprost concentration in residual solution was analyzed in a masked fashion, by reversed-phase high-performance liquid chromatography (HPLC). In all, 110 patients were enrolled and 89 returned their bottles. Sixty-nine bottles had sufficient residual volume to conduct HPLC analysis. All patients reported that bottles were stored at room temperature (average high from 70-95 degrees F during the daytime). The mean +/- SD latanoprost concentration measured in the residual solutions was 48.31 +/- 2.31 microg/mL. Ninety-four percent of the bottles had concentrations within 90% to 110% of the labeled amount. No difference in latanoprost concentrations was found between the bottles used for 4 weeks versus those used for 6 weeks. In an eye clinic setting, latanoprost ophthalmic solution 0.005% remains stable after 4 or 6 weeks of patient use from the same bottle when stored at room temperature.