bosentan

Bosentan is an oral endothelin receptor antagonist approved for the treatment of pulmonary arterial hypertension (PAH). It blocks endothelin-1 receptors (ETA and ETB), reducing vasoconstriction and vascular remodeling in the pulmonary arteries. By lowering pulmonary vascular resistance, bosentan can improve exercise capacity and symptoms in PAH patients.

Indications include idiopathic PAH, heritable PAH, and PAH associated with connective tissue diseases such as systemic sclerosis; it is approved for adults and, in some regions, for certain pediatric patients.

Administration and dosing: the usual starting dose is 62.5 mg taken twice daily for four weeks, followed by 125 mg twice daily if tolerated. Dosing may be adjusted based on hepatic function. Liver function tests must be monitored regularly during treatment.

Safety and monitoring: bosentan is contraindicated in pregnancy due to teratogenicity; women of childbearing potential must use two forms of contraception and have monthly pregnancy tests. It should not be used in significant hepatic impairment. Baseline and periodic monitoring of liver enzymes and bilirubin are required, as hepatotoxicity can occur. Common adverse effects include liver injury, edema, headache, flushing, and anemia.

Interactions and regulations: bosentan is a substrate and inducer of CYP3A4 and 2C9, so it can affect the levels of other drugs. It can reduce the effectiveness of certain hormonal contraceptives and interacts with various PAH therapies, requiring clinician oversight. Because of teratogenic risk, many countries require a risk-management program for its distribution (for example, the Tracleer program in the United States).