Prostacyclin therapy for pulmonary arterial hypertension: new directions.

Pulmonary arterial hypertension (PAH) is characterized by vasoconstriction and smooth muscle cell proliferation of the pulmonary arterioles, as well as in situ thrombosis of the small pulmonary arteries. Prostacyclin is involved in PAH vascular remodeling. It is unclear if decreased prostacyclin in the lungs is a cause or a consequence of PAH, but the relative lack of prostacyclin and its positive effects on the pulmonary vascular bed support the theory that long-term prostacyclin replacement is effective. Current therapies based on evidence-based medicine include epoprostenol, treprostinil, iloprost, and beraprost, each with limitations based on the drugs' inherent properties and administration route. Treatment of PAH by inhibiting multiple pathways concurrently may produce additive benefit. Because prostacyclin therapy is not curative and does not normalize pulmonary hemodynamics in the majority of cases, combining a prostacyclin with other PAH agents may be a promising approach.