Drugs Which May Inhibit Anticoagulant Effect and Decrease PT/INR

Major Effect	Moderate Effect	Minor Effect
Aminogluethimide Barbiturates (e.g. phenobarbital) Carbamazepine Cholestyramine Griseofluvin Nafcillin Rifampin	Azathioprine Cyclosporine Dicloxacillin Etretinate Methimazole Phenytoin Propylthiouracil	Chlordiazepoxide Sucralfate Trazadone