buprenorphine - when to reduce?

Hi,

Odie's been on buprenorphine since last Tuesday (6 days). He's getting 0.25mls every 8 hours.

It was prescribed for unknown pain at the base of his tail. X-rays, blood work, external exam, and rectal exam showed nothing unusual. But he was in considerable pain. The vet figured it was some sort of soft tissue injury, although I have no idea how it could have happened.

It's been helping, he's not in pain as far as I can tell. He's eating is back up. But he's still sleeping lots, I think it's making him groggy. His BG numbers are slightly lower since yesterday (they had gone up with the pain).

Should I move to every 12 hours instead of 8? Continue every 8 hours even though he's groggy? How do I know how long he needs it (other than stopping altogether and seeing what happens)?

Any advice?

Thanks
Odiesmom