Intravenous epoprostenol remains an important treatment for pulmonary arterial hypertension (PAH) but can only be given intravenously. Until recently the only formulation available to our patients (Flolan 10.5) was thermolabile and required daily preparation. In 2016, we transitioned all patients in our service to a new, thermostable formulation (Flolan 12). All patients in our unit using epoprostenol as of November 2016 were recruited to this prospective study which examined for safety issues and effects on QoL, 6MWD and serum NT-proBNP. We also collected qualitative data regarding activities of daily living. The transition process did not result in any clinical deterioration. There were no safety issues identified and all but one of the participants preferred the new formulation. We therefore conclude that transitioning patients from intravenous Flolan 10.5 to Flolan 12 is safe, does not lead to any clinical deterioration and is acceptable to patients for reasons of convenience.