| Summary: | **Background:** Pulmonary arterial hypertension (PAH) is a disease characterized by dyspnea, fatigue, chest pain and syncope. As there is no known cure for PAH, the goal of treatment is to control symptoms and slow disease progression. Sildenafil, a phosphodiesterase-5 inhibitor, has been indicated to improve exercise capacity in PAH in both the United States and the European Union since 2005; since 2009, it also has been indicated in the United States to delay clinical worsening. Patterns of sildenafil use in PAH
patients have not been reported.
**Objectives:** To describe patterns of treatment with sildenafil among commercially insured patients in the United States with PAH.
**Methods:** Using a large U.S. healthcare claims database, we identified all patients with evidence of PAH (International Classification of Disease, 9th Revision, Clinical Modification [ICD-9-CM] diagnosis codes 416.0, 416.8) and receipt of sildenafil between January 1, 2005 and September 30, 2008. The date of each patient’s earliest pharmacy claim for sildenafil was designated as his or her “index date”; patients with <6 months of data prior to this date were excluded. Post-index use of sildenafil was then examined in terms of the numbers of pharmacy claims and therapy-days, the medication possession ratio (MPR), and the incidence of therapy switching.
**Results:** We identified a total of 855 PAH patients who began sildenafil therapy and met all other entry criteria. Mean (standard deviation [SD]) follow-up was 423.4 (313.0) days. Over this period, these patients averaged 7.1 (6.8) (median, 5) pharmacy dispensings for sildenafil, representing 273.4 (254.8) therapy-days (median, 180). Mean MPR was 71% (median, 83%). Fourteen percent of sildenafil patients switched to another agent during follow-up.
**Conclusions:** In “real-world” clinical practice, many PAH patients beginning treatment with sildenafil remain on therapy for extended periods and are relatively compliant with treatment.
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