I am a 72 year old female, overweight , and lacking energy . I have had 3 knee replacements due to infection. Last December I was medivacced to Vancouver because a nuclear scan was showing signs of re infection. The Doctor with a panel of physicians decided that as they had tried to remove the binfection twice, and it had been reoccurring that there was no valid reason to operate again. After aspirating the knee it was decided to put me on cloxicilan IV for 6 weeks and then to use oral antibiotic to control the infection. I was put on 500mg x 4 keflex, which interfered with myINR. I have had 2. Pulmonary embolisms and have a vena cava filter in my vein . While I was on keflex my INR was all over the place. 1.9, so the dosage of warfarin was increased. The next week 3.8 to the dose was Reduced. The following week 1.9. At this point I asked whether the keflex was causing the difficulties. So the doctor switched me to penicillin V. I emailed my surgeon to ask if this was an acceptable alternate. He replied that it was not and said to go cloxicilan 4x daily. Now my question. I have a very sore and sensitive mouth and deep lesions on my tongue. Not totally raw, but very near to that. Is this caused by the antibiotics, and if so what can be done about it. If I have to go off the antibiotics I am in danger of the infection reoccurring, and was told that if the most conservative approach didn t work, then there were only two alternate treatments. Permanently straightening the leg by fusing the joint, or amputation . Neither of which thrill me. What can I do. I trust my surgeon, but am very doubtful of my G P. I am trying to change doctors, but being in a small community there are few choices.