This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Pharmacology), Subject name: Pharmacology
[{'content': 'Allopurinol specifically inhibits \nSelect and explain. \nA. Xanthine oxidase, B. Arginase, C. Carbamoyl transferase, D. Urease', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a (Xanthine oxidase). (Ref. Harrison\'s Medicine 18th /Chapter 359.)ALLOPURINOL# Allopurinol is competitive inhibitor of xanthine oxidase.# Specific treatment of uric acid calculi requires reducing the urine uric acid concentration with a xanthine oxidase inhibitor, such as allopurinol or febuxostat.# It leads to rise in levels of water-soluble compounds - xanthine & hypoxanthine.# It inhibits degradation of 6-MP & azathioprine & therefore their dose should be reduced by 75%.# It is used only in "Chronic gout"# It is contraindicated in pregnancy, lactation, & hypersensitive patients.', 'role': 'assistant'}]