If your lucky enough to live within a days drive or less of canada, you are fortunate enough to have access to a few OTC drugs in canada (Codeine, etc..). You can purchase tylenol/asprin with codeine for a few dollars over the counter. (you have to ask for them. they keep them behind the counter)

If I was to bring these across the border, I personally would empty out an 500ct asprin bottle and dump 400 or so in and throw it in my glovebox. And don't claim them. It is the simplest, easiest way.

I don't suggest doing this. It is what I myself would do if I lived near the border which I don't. I live in south africa. So don't go breaking any laws.