Patients with pulmonary arterial hypertension on long-term , stable epoprostenol therapy were transitioned from epoprostenol with glycine and mannitol excipients ( Flolan ; GlaxoSmithKline , Durham , NC ) to epoprostenol with arginine and sucrose excipients ( Veletri ; Actelion Pharmaceuticals Ltd , Allschwil , Switzerland ) .