This is actually funny because I was reading online earlier about
what to do with disposing of medicine. According to the article, you should mix them with something like coffee grounds to make them unpleasent and throw them out with your garbage. For narcotics you should flush them.
Now if you just don't want to waste the medicine, of course that is another story. Just remember they do have a shelf life so you may save them for a couple of years but if you use them again, they might not work.