Drug combinations

I am concerned that a friend is doing herself harm by taking drugs that may not be compatable.  She was prescribed coumadin and is also taking Zanax.  Don't these two drugs counteract each other?

[Cleveland Clinic, MD]

There are many drug interactions with coumadin but Zanax is not one of them.  Of course with all medications your doctor and pharmacist should be aware of all drugs you are taking.  Here is a list of some of the drugs that interact with coumadin.
Known Drug interactions with Warfarin
Increased Effect :

                       Highly Probable

                            Alcohol (if concomitant liver disease)
                            Amiodarone
                            Cimetadine
                            Clofibrate
                            Cotrimoxazole
                            Erythromycin
                            Fluconazole
                            Isoniazid
                            Metronidazole
                            Miconazole
                            Omeprazole
                            Phenylbutazone
                            Piroxicam
                            Propafenone
                            Propanolol
                            Sulfinpyrazone

                       Probable

                            Acetaminophen (Tylenol