"Medicine" may make your INR high, low, or do nothing to it. It depends on the type of medicine, how much you take, how long you take it, and your individual body. Generally speaking, don't stop taking Coumadin just because you are going to be on any other medicine, unless it is something like Heparin or Lovenox that is given in place of Coumadin. Talk to your cardiologist. Read Al's website. Educate yourself about how Coumadin works. It is a long acting medicine and shouldn't be started and stopped, or adjusted too often, or it will never work right.
Also, although 5.0 is high, I wouldn't consider it dangerously high. Just eat some green vegetables and it will back in range in no time.