The major pharmacological actions of treprostinil are direct vasodilation of pulmonary and systemic arterial vascular beds and inhibition of platelet aggregation. In addition to treprostinil's direct vasodilatory effects, it also inhibits inflammatory cytokine. As a synthetic analogue of prostacyclin, it binds to the prostacyclin receptor, which subsequently induces the aforementioned downstream effects.

Pulmonary arterial hypertension (PAH) is a disease in which blood pressure is abnormally high in the arteries between the heart and lungs. PAH is characterized by symptoms of shortness of breath during physical exertion. The condition can ultimately lead to heart failure. Treprostinil is a potent oral antiplatelet agent. The major pharmacologic actions of treprostinil are direct vasodilation of pulmonary and systemic arterial vascular beds and inhibition of platelet aggregation. In animals, the vasodilatory effects reduce right and left ventricular afterload and increase cardiac output and stroke volume. Other studies have shown that treprostinil causes a dose-related negative inotropic and lusitropic effect. No major effects on cardiac conduction have been observed.

Substantially metabolized by the liver, but the precise enzymes responsible are unknown. Five metabolites have been described (HU1 through HU5) however, the biological activity and metabolic fate of these are unknown. The chemical structure of HU1 is unknown. The metabolite HU5 is the glucuronide conjugate of treprostinil. The other metabolites are formed by oxidation of the 3-hydroxyoctyl side chain (HU2) and subsequent additional oxidation (HU3) or dehydration (HU4). Study results of in vitro human hepatic cytochrome P450 demonstrates that treprostinil does not inhibit CYP-1A2, 2C9, 2C19, 2D6, 2E1, or 3A. Whether treprostinil induces these enzymes has not been studied.

Symptoms of overdose are extensions of its dose-limiting pharmacologic effects and include flushing, headache, hypotension, nausea, vomiting, and diarrhea. Most events were self-limiting and resolved with reduction or withholding of treprostinil.