PTGIR and pulmonary arterial hypertension: In recent years, various forms of pulmonary vasoactive agents, including agents targeting prostacyclin pathway (e.g., inhaled prostacyclin analogues and prostacyclin receptor agonist), endothelin receptor antagonists, and nitric oxide pathway enhancers have been approved for the treatment of pulmonary arterial hypertension (group 1 pulmonary hypertension).