What drugs should not be give to patients who are taking warfarin?

Lots. Some antibiotics/antifungals, sulfa drugs, anti-inflammitory meds(advil, aleve, motrin, etc.), vitamin k, and of coarse any foods with vitamin k. Aspirin and Plavix also affect clotting but in a slightly different way. And this is NOT a complete list. There are some others I dont remember right now.