Hello again to all! As many on this forum know, rectal administration is a very efficacious and money-saving way to use many drugs. It is not without its safety pitfalls, but when dosage is reduced accordingly from an oral dose, it can be a way to get maximum bioavailability without IVing a substance. With pills in particular, rectal administration is far safer than IVing but can give the user comparable bioavailability in some cases. So, what I am wondering is, are there any opiates that are LESS bioavailabile than oral or insufflated routes when used rectally? Any opiates that just dont work at all rectally? If your I have any experiences to post, bioavailability percentages to put up, or any evidence one way or the other as to what CANT be used rectally or what doesnt work well, post this here! Many thanks to swiNicaine for providing the idea for this thread, when he noted that ambien does not seem to work as well rectally, and might even be a waste of drug. Granted, ambien is not an opiate, but you get the idea. If you can think of other drugs that are not well-absorbed rectally, perhaps a catch-all thread could be started in the pharmacology forum as an easy database that one could look to in order to avoid squandering products!