<prompt> 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:Increase the dose of warfarinReplace warfarin with acenocoumarinSwitch ethambutol for rifampicinUse LMW heparin  <response>: 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 