Review Question - QID 106865

This patient was diagnosed with pulmonary artery hypertension (PAH). Bosentan is an endothelin receptor antagonist which is used to treat PAH.

Endothelin is a potent vasoconstrictor and also acts to stimulate vascular smooth muscle cell proliferation. Current evidence suggests endothelin is involved in the pathophysiology of PAH. Bosentan is an antagonist of endothelin receptors, which decreases pulmonary vascular resistance, thereby reducing pulmonary artery hypertension.

Stringham and Shah discuss the diagnosis and management of PAH. Treatment options may vary depending on the underlying etiology, but commonly include oral anticoagulants, diuretics, oxygen supplementation, and sometimes calcium channel blockers. New treatment options include endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and prostacyclin analogs. Interventional procedures may be useful in refractory cases, and may include balloon atrial septostomy or lung transplant.

Chester and Yacoub discuss the role of endothelin in PAH. Control of pulmonary vascular tone is a multi-factorial process. Three molecules are known to regulate the diameter of pulmonary vasculature. Two molecules, namely nitric oxide and prostacyclin, act to increase the diameter. One molecule, endothelin, is responsible for vasoconstriction.

Illustration A is a schematic showing the mechanism of endothelin in increasing pulmonary vasculature tone.

Incorrect Answers:
Answer 2: Endothelin receptor agonism would worsen PAH.
Answers 3-5: These are all mechanisms of medications that can be used in the treatment of PAH, but they are not the mechanism of bosentan.