Bosentan (BST)

Bosentan is a dual endothelin receptor antagonist used in the treatment of pulmonary artery hypertension (PAH). Bosentan is a competitive antagonist of endothelin-1 at the endothelin-A (ET-A) and endothelin-B (ET-B) receptors. Under normal conditions, endothelin-1 binding of ET-A or ET-B receptors causes constriction of the pulmonary blood vessels. By blocking this interaction, bosentan decreases pulmonary vascular resistance. Bosentan has a slightly higher affinity for ET-A than ET-B. Bosentan use requires hematocrit monitoring due to potential onset of anemia. Hormone-based contraception is not possible in women taking Bosentan, due to a pharmacokinetic interaction. Therefore, other highly reliable forms of contraception should be used instead. Bosentan is contraindicated in pregnancy because of its teratogenicity (Pregnancy Category X).