Patients with pulmonary arterial hypertension (PAH) are often treated with parenteral prostanoids. Continuous infusion of parenteral prostanoids comes at the cost of increased risk of thromboembolism, bloodstream infections, and inconvenience to patient lifestyle. Patients with stable symptoms may be transitioned to an oral formulation of prostanoids. This transition has been accomplished safely over 5 days in prior studies. We present a protocol for safe and efficient transition from parenteral to oral prostanoids within 24 hours. METHODS:We selected patients diagnosed with PAH who were started on continuous parenteral prostanoid therapy and subsequently stabilized symptomatically. Patients were electively admitted to the hospital for transition. The initial total daily dosage (TDD) of oral treprostinil was determined using the following equation: Oral treprostinil total daily dose (in mg) ¼ 0.0072 x parenteral treprostinil rate (in ng/kg/min) x weight (in kg). The TDD/3 yields the dose for three times daily dosing. Patients were transitioned off parenteral and onto oral treprostinil therapy within 24 hours using the following transition protocol.