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
Warfarin effect may be enhanced by: March 2005 
Select and explain. 
A. Phenobarbitone, B. Ketoconazole, C. Rifampicin, D. Chronic alcoholism
D: Chronic alcoholism
Answer: D: Chronic alcoholism 
Explanation: Ans. D: Chronic Alcoholism Many commonly-used antibiotics, such as metronidazole or the macrolides, will greatly increase the effect of warfarin by reducing the metabolism of warfarin in the body. Other broad-spectrum antibiotics can reduce the amount of the normal bacterial flora in the bowel, which make significant quantities of vitamin K, thus potentiating the effect of warfarin. In addition, food that contains large quantities of vitamin K will reduce the warfarin effect. Thyroid activity also appears to influence warfarin dosing requirements; hypothyroidism (decreased thyroid function) makes people less responsive to warfarin treatment, while hypehyroidism (overactive thyroid) boosts the anticoagulant effect. Liver diseases, chronic alcoholism may enhance effect as synthesis of clotting factor may be deficient.