Actually, I've wondered that myself Sham. About amphetamine and methamphetamine specifically. I believe, off the top of my head, that approximately 50% of methamphetamine is excreted unchanged into the urine; about 15% of amphetamine is as well.So yes. If you're that desperate and that broke, you could make your meth last about twice as long by drinking your own urine. But even I've never been *that* desperate... extracting it might be possible, but I never bothered looking into it. Most drugs aren't excreted unchanged though, so it wouldn't do you much good to try putting what comes out back into you for the most part.