The Effect of Combination Pharmacotherapy on the Prescription Trends of Glaucoma Medications

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Abstract
To describe prescription trends within a managed care setting for glaucoma medications and to examine the effect of introduction of Cosopt® -a fixed combination of dorzolamide and timolol. All prescriptions dispensed to any of the 470,350 members of an Israeli health maintenance organization were monthly scanned for patients treated for glaucoma, between January 2000 and May 2003. The monthly mean number of glaucoma patients was 3899 ± 104 (mean ± SD). All topical glaucoma prescriptions were documented, and the monthly prescription rate of each medication was calculated and plotted. The monitored glaucoma medications were: β-adrenergic antagonists, dorzolamide, latanoprost, pilocarpine, brimonidine, Cosopt®, and others. β-adrenergic antagonists were the top prescribing drug (>35% of all glaucoma prescriptions). The prescription rates of pilocarpine and β-adrenergic antagonists were in constant decline, while latanoprost and brimonidine increased steadily. The introduction of Cosopt® changed the prescription trends of dorzolamide from increasing to rapidly decreasing, and accelerated the long-term decline of β-adrenergic antagonists. Concomitant with the introduction of Cosopt® the prescription rate of β-adrenergic antagonists temporarily increased. This was due to a total increase in glaucoma prescriptions. When Cosopt® was introduced, 37.5% of patients were prescribed Cosopt® together with β-adrenergic antagonists, and 16.5% also received dorzolamide. Thereafter the co-prescription decreased steadily. Introduction of a combination drug should be accompanied by physicians', pharmacists', and patients' education to prevent its inappropriate usage together with its components.