Purpose To assess possible changes in medication adherence to prostaglandin analog (PGA) regimens among patients with open-angle glaucoma (OAG) after the initial introduction of generic PGAs. Design Longitudinal cohort analysis. Participants Patients older than 40 years with OAG continuously enrolled in a nationwide managed-care network during 2009-2012 who used PGAs. Methods Mean adherence rates were calculated for topical PGA use during the 18 months before the introduction of generic latanoprost (September 2009-February 2011) and the 18 months after generic latanoprost became available (July 2011-December 2012). The rates were compared between persons who continued to use brand-name PGAs once generic latanoprost became available and others who switched to generic latanoprost. Multivariable logistic regression identified variables associated with an improvement or worsening of adherence of ≥25%. Main Outcome Measures Mean adherence rates and odds of 25% or more improved or worsened adherence (with 95% confidence intervals [CIs]). Results A total of 8427 patients met the study eligibility criteria. Compared with persons switching to generic latanoprost, patients who continued taking brand name PGAs were 28% less likely to have improved adherence (odds ratio [OR], 0.72; 95% CI, 0.55-0.94) and 39% more likely to have reduced adherence (OR, 1.39; 1.04-1.86) of ≥25%. Improved adherence after the generic drug's introduction was also associated with higher monthly medication copay in the pregeneric period (P = 0.02), lower copay after introduction of the generic drug (P < 0.0001), and black race (OR, 1.25; 95% CI, 1.04-1.50). Six-hundred twelve patients (7.3%) discontinued all antiglaucoma interventions when generic latanoprost became available. Conclusions Given that cost can significantly deter adherence, switching patients to generic medications may help improve patients' drug-regimen adherence. A considerable number of patients discontinued glaucoma drug use altogether when generic latanoprost became available. Ophthalmologists should work with insurers and pharmacists to prevent such discontinuation of use as generic forms of other PGA agents become available.
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