Bosentan for the Treatment of Pulmonary Arterial Hypertension

OBJECTIVE: To describe the pharmacology, pharmacokinetics, efficacy, and safety of bosentan in the treatment of pulmonary arterial hypertension (PAH). DATA SOURCES: A MEDLINE and Current Contents search (1966-June 2002) of the English-language literature was conducted to identify published dose-ranging, pharmacokinetic, pivotal efficacy trials and review articles of bosentan and endothelin antagonists. Additional references were identified from the bibliographies of the retrieved articles. DATA SYNTHESIS: Bosentan is the first orally active, nonpeptide endothelin receptor antagonist approved by the Food and Drug Administration for use in patients with World Health Organization (WHO) functional class III and IV PAH. Titrated to a dose of 125 mg twice daily, bosentan produces pulmonary vasodilation, improving cardiopulmonary hemodynamics leading to better outcomes for patients. It is metabolized primarily by the hepatic system via the cytochrome P450 enzyme pathway and eliminated by biliary excretion. Bosentan is an inducer of the isoenzymes CYP3A4 and 2C9. It possesses a unique pharmacokinetic profile with a terminal elimination half-life of approximately 5 hours, yet steady-state plasma concentrations are not achieved for 3-5 days as a result of enhanced drug clearance and autoinduction following multiple daily dosing. The major adverse effects of bosentan are the potential for birth defects and hepatotoxicity. CONCLUSIONS: The use of bosentan in patients with WHO functional class III and IV PAH is associated with improved exercise tolerance, cardiopulmonary hemodynamics, and increased time to clinical worsening when compared with placebo. It offers significant advantage in ease of administration and quality of life compared with epoprostenol therapy, with similar efficacy.