Anticoagulants: Phenobarbital lowers the plasma levels of dicumarol (title Beforehand used: bishydroxycoumarin) and will cause a minimize in anticoagulant action as measured with the prothrombin time. Barbiturates can induce hepatic microsomal enzymes leading to enhanced metabolism and diminished anticoagulant response of oral anticoagulants (e.DRU