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': 'The anticoagulant action of warfarin is potentiated by all except: \nSelect and explain. \nA. Phenylbutazone, B. Vitamin K, C. Rifampicin, D. 2 & 3', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A. Enhanced anticoagulant action\n\nBroad-spectrum antibiotics: Inhibit gut flora and reduce Vit K Production.\nSome cephalosporins (ceftriaxone, cefoperazone) cause hypoprothrombinaemia by the same machanism as warfarin-produce additive action.\nAspirin: Inhibits platelet aggregation and causes g.i. bleeding-this may be hazardous in anticoagulated patients. High doses of salicylates have synergistic hypoprothrombinemic action and also displace warfarin from protein binding site.\nLong acting sulfonamides, indomethacin, phenytoin and probenecid: displace warfarin from plasma protein binding.\nChloramphenicol, erythromycin, celecoxib, cimetidine, allopurinol, amiodarone and metronidazole: inhibit warfarin metabolism.\nTolbutamide and phenytoin: Inhibit warfarin metabolism and vice versa.\nLiquid paraffin (habitual use): Reduces vit K absorption.\n\nB. Reduced anticogulant action\n\nBarbiturates (but not benzodiazepines). Carbamazepine, rifampin and griseofulvin induce the metabolism of warfarin. The dose of anticoagulant determined during therapy with these drugs would be higher: if the same is continued after withdrawing the inducer-marked hypoprothrombinemia can occur-fatal bleeding is on record.\nOral contraceptives: Increase blood levels of clotting factors. The important features of heparin and warfarin are compared.\n\nReference: Essentials of Medical Pharmacology Eighth Edition KD\xa0TRIPATHI\xa0page no 670', 'role': 'assistant'}]