This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Bostentan is a - \nSelect and explain. \nA. Serotonin uptake inhibitor, B. Endothelin receptor antagonist, C. Leukotriene modifier, D. Calcium sensitizer', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Endothelin receptor antagonist Endothelin receptor antagonists o There are two endothelin receptor subtypes - ETA and and ETB. o Bosentan is a nonselective endothelin antagonist - blocks both ETA and ETB. o Bosentan is active intravenously and orally. o Bosentan is currently approved for use in pulmonary hypeension. Tezosentan another nonselective antagonist is used investigation for the treatment of acute hea failure. o Sitaxentan and ambrisentan are selective ETA antagonists. o Phosphoramidon inhibits formation of endothelin by inhibiting endothelin conveing enzyme. Remember o Bosentan can cause severe hepatotoxicity - monthly liver function tests should be done. o It is contraindicated in pregnancy.", 'role': 'assistant'}]