Treprostinil is a synthetic prostacyclin analogue with antiplatelet and 
vasodilatory properties. It is the only prostacyclin analogue with different 
options of delivery, i.e. subcutaneous, intravenous, inhaled or oral. 
Subcutaneous treprostinil has been shown in short- and long-term studies to 
improve exercise capacity, functional class, haemodynamics and survival in 
patients with pulmonary arterial hypertension (PAH). Pain at the infusion site 
has been a major drawback of subcutaneous treprostinil, hampering dose 
titration, and ultimately leading to increased discontinuation rates. The 
additional clinical interest in treprostinil as an alternative intravenous 
prostacyclin has developed due to its favourable properties, including longer 
half-life, chemical stability, the possibility of intravenous infusion without 
the need for ice packs, and easy drug preparation. Intravenous treprostinil 
improves exercise capacity, functional class and haemodynamics in patients with 
PAH, over the period of 12 weeks. If patients are switched to intravenous 
treprostinil, they usually need to double the dose to attain the same efficacy. 
Whether the effect of intravenous treprostinil remains clinically relevant 
beyond 12 weeks is not known, and a longer follow-up would be required to 
investigate this. Inhaled treprostinil is an efficacious treatment in PAH 
patients who are moderately symptomatic on background oral therapy. Oral 
treprostinil on top of background therapy did not lead to an improvement in 
6-minute walking distance after 16 weeks of treatment.