They definately ask you "what, if any, involvement have you had with drugs". I'm sure it's one of the standard questions, just like the one about whether you've been in trouble with the law. I don't think that it will be a problem being honest about it in this case. This is simply because you've already let the cat out of the bag. Normally I would certainly recommend keeping it under wraps.
Anyway, good luck!
TMA