Poor Adherence to PDE-5i Linked to Adverse Effects in PAH Patients, Study Finds

Adverse effects are associated with poor adherence to phosphodiesterase-5 inhibitors (PDE-5I) as treatment for patients with pulmonary arterial hypertension (PAH) treated via an integrated care model at an academic institution. Hospitalization events, out-of-pocket costs and frequency of dosing did not play a role, a study shows.

Led by researchers at Tennessee’s Vanderbilt University Medical Center, the study, “High Rates of Medication Adherence in Patients with Pulmonary Arterial Hypertension: An Integrated Specialty Pharmacy Approach,” was published in the journal PLOS ONE.

PAH is a rare, progressive disorder characterized by high blood pressure (hypertension) in the arteries of the lungs. It manifests in shortness of breath (dyspnea), especially during exercise; fatigue, chest pain, and fainting.

Phosphodiesterase-5 inhibitors (PDE-5I), such as Revatio (sildenafil) and Adcirca (tadalafil), have demonstrated benefits for PAH patients, including eased symptoms and improved quality of life. Still, some studies have found that less than half of patients prescribed a PDE-5I were adherent after six months.

Researchers aimed to investigate the causes for this, in the context of an integrated pharmacy practice model implementing interdisciplinary team-based care. In this model, pharmacists are embedded in the clinic to assist with insurance approval, patient counseling, and management of adverse effects, with the goal of improving patient outcomes.

The study enrolled 131 patients (70% females, median age 55 years) who were followed for over two years. More than half (62%) were non-smokers and 71% had government-funded insurance. Of all participants, 89% had mild to moderate functional impairment, being classified as functional class II or III. This classification includes four classes and is used to rate how ill patients are (class I: least sick; class IV: most sick).

Sixty-six percent of patients were treated with Adcirca and 33% with Revatio.

A review of patients’ clinical records and pharmacy claims showed that the integrated model was associated with high overall adherence rates, with 94% of patients taking the prescribed PDE-5I 80% or more of the time.

However, eight patients had lower treatment adherence levels. These patients were more likely to have reported an adverse reaction. The most common events reported were headache (24%), reflux (11%), diarrhea (11%), leg pain (6%), and nausea or vomiting (5%).

In contrast, hospitalization events, out-of-pocket costs (median of $.62; ranging from $0 to $354.71), and frequency of dosing were not found to be associated with adherence to PDE-5I therapies.

Although this study included a small group of patients, “[those] receiving care within the high-touch, integrated model maintained high rates of medication adherence over a two-year period,” researchers said.

Additional studies are still warranted to further explore the impact of this integrated care model on improving PAH patients’ adherence to therapy when prescribed dual or triple treatment regimens, common among this population, they said.