Poor guy. Buprenex can cause respiratory depression, but I wouldn't expect it to last that long after not giving him the drug. I know in humans if an opiod overdose is suspected (leading to respiratory depression) they can administer nalmefene (trade name Narcan) to reverse its effects. I don't know if they do this to animals. The main use of the Narcan is in acute opiod overdose by people that abuse opiods, so it probably isn't commonly used in veterinary medicine. I assume you could use it off-label with dosing guidelines that were set forth in the original safety and/or efficacy pre-clinical studies done by the drug company, but that would require a lot of research to uncover those studies, and they may not have initially tested it in rabbits (although it's likely).
Also important to note is that buprenorphine (buprenex) is metabolized by CYP3A4, meaning that there's a specific enzyme in the liver called cytochrome P450 3A4 isoform that breaks it down. Some other drugs can inhibit CYP3A4. Metacam is not one of them, but you may want to check with the vet or read the labels of any other medications he's on to make sure they're not CYP3A4 inhibitors. If CYP3A4 is inhibited, the levels in his system could be too high.
As bad as this sounds, it's better for it to be a buprenorphine overdose than some other cause of respiratory depression. It could be due to swelling or another abscess causing airway constriction that he's not getting enough O2. I really hope the O2 treatment will turn him around and the vet can figure out what's causing this.
Huge hugs and positive thoughts sent your way. I'm really pulling for him to make it through this.
ray:
