CoQ taken as a pharmacological substance has potential to inhibit the effects of theophylline as well as the anticoagulant warfarin; CoQ may interfere with warfarins actions by interacting with cytochrome p450 enzymes thereby reducing the INR, a measure of blood clotting. The structure of CoQ is similar to that of vitamin K, which competes with and counteracts warfarins anticoagulation effects. CoQ is not recommended in people taking warfarin due to the increased risk of clotting.