PURPOSE: Pulmonary arterial hypertension (PAH) requires chronic pharmacologic therapy and published adherence data are limited on use of phosphodiesterase type 5 inhibitors (PDE5Is) in clinical practice. This study assessed factors associated with adherence to PDE5Is for the treatment of PAH.
METHODS: We analyzed pharmacy claims from Medco between 01/2008-12/2010. Patients were selected if they had at least one claim for sildenafil or tadalafil (PAH-indicated brands only) between 05/2009-05/2010. Patients naïve to PDE5Is during 12 months prior to the index date (date of first prescription) were included. Patients were considered adherent if their proportion of days covered (PDC) was ≥80% over a six month period. Logistic regressions were estimated to assess factors associated with adherence. Analyses were performed stratified by use of a specialty pharmacy (SP) or retail pharmacy (RP).
RESULTS: The study included 2,143 patients (mean age: 65 years; 65% female), of which 1,817 were prescribed sildenafil (approved dose 20mg thrice-daily) and 326 were prescribed tadalafil (approved dose 40mg once-daily). Forty-seven percent of patients were adherent to PDE5Is, and adherence was significantly higher among tadalafil (60.7%) than sildenafil users (44.3%, p<0.001). Adherence was higher among 930 SP users (65.6%) than 1,213 RP users (32.3%, p<0.001). Twenty-seven percent of patients received their index prescription from a pulmonologist, 23% from a cardiologist, 17% from primary care provider, and the rest from other or unknown specialty. Among RP users, evaluation of adjusted regressions revealed that factors associated with higher adherence were: use of tadalafil (OR=2.62; 95% CI: 1.61-4.24) and prescription from pulmonologist (OR: 1.68; 95% CI: 1.14-2.47). Similar associations were not observed among SP users.
CONCLUSIONS: In clinical practice, adherence to PDE5Is for PAH is sub-optimal.
CLINICAL IMPLICATIONS: Our findings suggest enhanced adherence to PDE5Is in patients with PAH is associated with simpler dosing frequency, use of SP, and index prescription by a pulmonologist.
DISCLOSURE: Aaron Waxman: Consultant fee, speaker bureau, advisory committee, etc.: Aaron Waxman is an investigator and scientific advisor to United Therapeutics
Shih-Yin Chen: Consultant fee, speaker bureau, advisory committee, etc.: Shih-Yin Chen is an employee of United BioSource Corporation, which was contracted by United Therapeutics to work in collaboration on this study.
Luke Boulanger: Consultant fee, speaker bureau, advisory committee, etc.: Luke Boulanger is an employee of United BioSource Corporation, which was contracted by United Therapeutics to work in collaboration on this study.
Gil Golden: Employee: Gil Golden is an employee of United Therapeutics.
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