Im a cardiac patient had a mitral valve replacement and on warfarin. my throat is sore for the 3rd week now and the antibiotics i was using from the doc is not working. what now?

Re-evaluation.: You need to be seen by your doctor again for a couple of reasons. First, you remain symptomatic after the first line of treatment and therefore entertainment of second line treatment or alternate diagnosis needs to be made. Second, there are many medications that interact with warfarin and it would be unsafe to simply treat without being able to monitor your blood test for influence upon warfarin.