I am currently using buprenorphine and I have also methadone waiting there. Normally I use Tramadol but sometimes I change it to buprenorphine for a while as it is cheaper. But tramadol is more beneficial for me.
Anyway, I have the same problem and when I start methadone I will use naltrexone. I have this problem with buprenorphine too that it doesn't give the effects it used to (sedation, euphoria). So when that happens, my protocol is that for a while I increase naltrexone dose to inhibit agonist functions to the border of precipitated withdrawals. If you don't need instant fix for this problem but can wait few days (or weeks) then my advice is ultra low dose naltrexone and low dose naltrexone combined with the agonist.
I first start with a dose about 100-250ug at night. Then I increase it to 350ug next day. Then 450ug and up to 750ug which is the point when withdrawals start to noticeable happen. Sometimes I do so that I take 100ug every 1 hour. When withdrawals come too much then I stop. And then I repeat that the next day. Then I do like a that for a while and suffer a little bit and then just stop the naltrexone and voila, the opioids work again with smaller doses.
Now I am propably starting to reduce buprenorphine and change it to Methadone or Tramadol after withdrawal. What I am going to do is lower the dosage of buprenorphine while simultaneously increasing the dose of naltrexone daily as previously explained. That way the withdrawal is dealt much faster and tolerance reduced much faster.
I start it next week. I can report here how it works exactly if people are interested to hear?