This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hematology, Subject name: Pharmacology
A diabetic female on INH and rifampicin for TB developed DVT.She was staed on warfarin, PT is not raised, and next step should be: 
Select and explain. 
A. Increase the dose of warfarin, B. Replace warfarin with acenocoumarin, C. Switch ethambutol for rifampicin, D. Use LMW heparin
D: Use LMW heparin
Answer: D: Use LMW heparin 
Explanation: Rifampicin is a microsomal enzyme inducer and hence enhances the metabolism of warfarin. Hence warfarin can be replaced with a LMWH as the treatment is to stop warfarin. Acenocoumarin is a coumarin derivative similar to warfarin. From medical pharmacology padmaja 4th edition Page no 339,340