Terguride (INN) is a serotoninantagonist. It is used for the treatment of hyperprolactinemia. Terguride is an oral, potent antagonist of 5-HT2B and 5-HT2A (serotonin) receptors. Serotonin stimulates the proliferation of pulmonary artery smooth muscle cells, and induces fibrosis in the wall of pulmonary arteries. Together, this causes vascular remodeling and narrowing of the pulmonary arteries. These changes result in increased vascular resistance and PAH. Due to the potential anti-proliferative and anti-fibrotic activity of terguride, this potential medicine could offer the hope of achieving reversal of pulmonary artery vascular remodeling and attenuation of disease progression.