To be honest, I was genuinely interested. Interestingly enough, the only top 10 school that drug tests seems to be WUSTL, and since they give you advance notice it is more of a common sense test.
I'm also disappointed at the response here, albeit not surprise. Most of the average premeds I've met throughout my career have been very hard working "straight shooters" that make it their crusade to look down upon anyone that does not adhere to their code of conduct.
You don't go to class? You party on the weekends? OMG you are never going to get into a medical school (lol...). I'm not saying this discipline is a bad thing, but there seems to be some inherent need to compensate for something... In contrast, I've rarely met a top candidate that is so close minded.
Personally, I think physicians must have an open mind and the ability to question the norm. Hell, there are way too many examples in history of unnecessary procedures carried out for the sake of following the established rules.
For those open minded individuals, following a redditor's advice, google "site:.edu medical students drug test".