antagonists, and include : liver enzyme abnormalities (increased ALT and AST) headache edema constipation nasal congestion upper respiratory tract infection dizziness insomnia flushing Because sitaxentan inhibits metabolism of warfarin, a decreased dose of warfarin is needed when co-administered with sitaxentan. This is because warfarin acts to prevent blood from clotting, and if it remains unmetabolized, it can continue to thin the blood. References External links https://www.drugs.com/nda/thelin_050714.html Mucke HAM: Sitaxsentan for the Oral Treatment of Pulmonary Arterial Hypertension: Benefits from Endothelin Receptor Subtype Selectivity? Clinical Medicine: Therapeutics 2009:1 111–121. ATS 2005. The International Conference of the American Thoracic Society. 20–25 May 2005. San Diego, CA. Robyn J. Barst, MD; Stuart Rich, MD, FCCP; Allison Widlitz, MS, PA; Evelyn M. Horn, MD; Vallerie McLaughlin, MD and Joyce McFarlin, RN : Clinical Efficacy of Sitaxsentan, an Endothelin-A Receptor Antagonist, in Patients With Pulmonary Arterial Hypertension Chest. 2002;121:1860-1868. American Heart Association. Primary or Unexplained Pulmonary Hypertension Benzodioxoles Chloroarenes Endothelin receptor antagonists Hepatotoxins Isoxazoles Sulfonamides Thiophenes Withdrawn drugs