Try cimetidine or a tall glass of grapefruit juice. Works like a charm, especially with hydrocodone. I take 400mg cimetidine religiously with any opiate I take. I'm convinced it results in a much stronger high. It also might help with some accompanying nausea that may result from the opiates.
Another cool thing I've found as of yesterday, is that ranitidine (Zantac) also works.