西他生坦钠

西他生坦钠为一种小分子化合物，主要通过抑制内皮素(Endothelin) 的作用而产生治疗作用（内皮素能调节血管收缩及血管平滑肌的生长）。其对内皮素A受体的作用是对B型内皮素受体作用的6500倍，高选择性的内皮素A受体拮抗剂能增加血流与反转血管收缩。Sitaxentan sodium是一种选择性的endothelin A receptor (ETA)(内皮素受体A）拮抗剂，IC50和K_i分别为1.4 nM和0.43 nM，比作用于ETB选择性高7000倍。Phase 3。Sitaxentan sodium inhibits ET-1-induced stimulation of phosphoinositide turnover with a K_i of 0.69 nM and a pA2 of 8.0.Sitaxentan sodium has a serum half-life in the rat and the dog of 6 hours - 7 hours and 60−100% oral bioavailability. Orally administered Sitaxentan sodium is rapidly absorbed in both the rat and the dog with a t_1/2(abs) of 0.7 hours and 0.3 hours, respectively. Peak plasma concentrations occurred between 2 hours and 3 hours postdosing in the rat and between 45 minutes and 90 minutes in the dog. The pulmonary vasoconstrictor response to acute hypoxia (10% O₂ for 90 minutes) is prevented with Sitaxentan sodium (5 mg/kg infused i.v. 10 minutes prior to the onset of hypoxia). Sitaxentan sodium delivered i.v. 50 minutes after the onset of hypoxia reverses the established pulmonary vasoconstriction. Sitaxsentan blocks increased plasma endothelin levels. Sitaxsentan dose dependently (10 mg/kg and 50 mg/kg per day in the drinking water) attenuates right ventricular systolic pressure, right heart hypertrophy, and pulmonary vascular remodeling observed 3 weeks after a single subcutaneous injection of monocrotaline. Systemic administration of the ETA receptor antagonist Sitaxentan sodium significantly attenuates cerebral vasospasm after subarachnoid hemorrhage (SAH). Sitaxentan sodium reduces the development of hypoxic pulmonary vasoconstriction (HPV) in the pig. In addition, bolus injection of Sitaxentan sodium reverses already established HPV.

西他生坦钠常见的不良反应为头痛、外周水肿。