Dude the oral bio-availability of zolpidem is something like 99% or something like that, and it onsets in about 10 minutes even with food in the stomach, seriously!! Snorting is fun because it provides a rush, but I actually think the overall buzz is weaker when snorted! Rectally, I have no idea why you'd want to do this when oral is probably as good if not better, but hey TEHO.
As a matter of fact, in the past I've noticed that when I snort ambien, I can go through 3 or 4 10mg pills in a few hours, nice rush every time, no problems, hang out, have fun, talk to friends, smoke weed, watch TV, whatever. One single 10mg pill taken orally will make me completely delirious and incoherent, I'll forget everything I did, lose inhibitions, have full on conversations with inanimate objects, take my clothes off and run around the house, etc.. It's strange...
Careful with that stuff. It's really, really fucking scary when you wake up in the morning, knowing you took ambien, and you find out you did all sorts of things like drive to the store, call family, rearrange things in the house, and worst of all, find your ambien bottle half empty and absolutely no recollection of anything.