Objectives: To assess factors associated with adherence to phosphodiesterase type 5 inhibitors (PDE5Is) in the management of pulmonary arterial hypertension (PAH).
Methods: This study analyzed pharmacy benefit claims of naïve Adcirca and Revatio users between January 1, 2008 and December 31, 2010. Patients were considered adherent if their proportion of days covered (PDC) was ≥ 80% over a 6-month period. Logistic regressions were estimated to assess the factors associated with adherence. Analyses were stratified by use of a specialty pharmacy or retail pharmacy. A sensitivity analysis was performed by excluding individuals with 90-day supply.
Results: Of the total of 2143 patients included, 46.8% were adherent. Adherence was higher among 930 specialty pharmacy users (65.6%) than 1213 retail pharmacy users (32.3%, p < 0.001). Adherence was higher among Adcirca users (60.7%; approved dose 40 mg once-daily) than Revatio users (44.3%, p < 0.001; approved dose 20 mg thrice-daily). Among retail pharmacy users, adherence was higher in patients using Adcirca (OR = 2.59; 95% CI = 1.60-4.22) and patients with an index prescription given by pulmonologists (OR = 1.70; 95% CI = 1.15-2.50), while lower in patients with higher copayment ($51-$250: OR = 0.61, 95% CI = 0.42-0.90; $251+: OR = 0.57, 95% CI = 0.39-0.83). Among specialty pharmacy users, only high copayment ($251+: OR = 0.56, 95% CI = 0.35-0.90) was found to be a significant factor for non-adherence. After excluding individuals with 90-day supply, adherence rate was 29.6% in retail pharmacy and 57.9% in specialty pharmacy (p < 0.001), and regression results were similar.
Limitations: Diagnosis of PAH was not confirmed without access to medical claims. Pharmacy refill records might not reflect actual consumption. Adherence evaluated for 6 months might not be generalizable to longer periods.
Conclusion: Adherence to PDE5Is for PAH is sub-optimal. The findings suggest that adherence to PDE5Is in patients with PAH is associated with the use of specialty pharmacy, simpler dosing frequency, a lower financial barrier, and a prescription given by pulmonologists.