But, as doctors soon discovered, between 40 and 99 percent of penicillin injected into patients isn't processed, and comes out in their urine. You can see where this is going: the resource-strapped doctors took to harvesting unused penicillin from patients' pee and re-injecting it.
Of course, as war ended and we got better at making (and injecting) penicillin, doctors simply manufactured enough, and stopped with the whole Bear Grylls impression. But as Smithsonian points out, taking up the practice again might not only be more efficient, but more friendly to the ecosystem, as fewer chemicals end up in rivers. For the time being, though, drinking your own piss whilst on antibiotics is still not advised.
source: gizmodo.com by Chris Mills