For what it's worth in the interest of harm reduction I thought I'd add some information for those who aren't obtaining their Buprenorphine through pain medication clinics (or don't mind where they obtain it) and wish to reduce the harm they're doing when injecting it that's inherent even after filtering pills for injection.
Transtec patches - I can't speak for any other brand of patches but Transtec Buprenorphine transdermal patches are widely used for IV here because they contain few or no water soluble fillers and so you can prepare a solution that is almost entirely just Buprenorphine and water, and then filter it for extra safety.
So how do you extract a patch? Simple, Transtec patches come in various different sizes, from 10mg to 40mg, with different microgram per hour release rates - the release rate is irrelevant though without getting into price discussion in my experience the larger patches tend to be available at a cheaper price per milligram.
Once you have your patch, you'll see it's attached to foil, and that in the middle in a raised bump - that's the matrix that contains all of the active Buprenorphine. What you want to do is take a piece of paper, cut it to the exact/almost exact size of the matrix, and using a ruler divide it into equal sections equivalent to the amount of milligrams in the patch - for example 40 equal sections if you have a 40mg patch. Now overlay this paper over the patch and cut off a segment, I'd suggest starting low since you'd be surprised how much stronger low doses of Buprenorphine can be, for example 0.25mg IV in my past experience has been more potent than 8mg sublingual. So for example cut out a 1mg segment, then cut off all the extra sticky part around the segment with the matrix since the sticky section around the side contains no active ingredient.
Once you have your 1mg, you can divide it into smaller doses, like I said I'd recommend starting off with 0.25mg even if you have a tolerance just to get a feel for Bupe IV, 0.25mg of pure Buprenorphine IV will also produce greater effects than 0.25mg of Buprenorphine in Suboxone IV, I'm not 100% certain why but it's possible that Naloxone blocks Norbuprenorphine and/or other active metabolites of the Bupe (at low doses there isn't enough Buprenorphine to block other actives, but any amount of Naloxone will). If you've already IVed Bupe in the past at low doses and it didn't work for you then you can start higher, but if you haven't tried a low dose, even if you've been IVing higher doses for a long time now I'd still recommend starting in the 0.25-0.5mg range and seeing for yourself, low doses really can be stronger. So cut your segment into the appropriate size for whatever dosage you want to take (i.e. if you want to IV 1mg just cut out 1mg, if you want to IV 0.25mg then cut out 1mg and cut out 1/4 of that, or just cut out 1/4 of that to begin with)
Separate it from the foil, and if you're careful, with a knife or scissors you can remove the patch coating which should reveal a thin strip of clear plastic. To extract the Buprenorphine you'll need around 1ml of water per 1mg you extract, but it's advised to use 1-2ml of water even for smaller amounts just because with water the extraction process can take a long time and you don't want your water evaporating leaving you with nothing to inject.
Leave the solution for between 1 to 24+ hours in a sterile environment where bacteria won't form in the solution (there are various things you can add to the solution to sterilise it if necessary) - the longer you leave it the more of the Bupe you'll extract, normally if you were extracting for another ROA you'd mix the water and make a half water half ethanol solution and the extraction would be done in 1-2 hours, but with IV you don't want to be injecting 50% ethanol, and with water it can take up to 24+ hours to get the full amount out, though you can just put a larger amount of the patch in (i.e. 2mg if you want to dose 0.25mg and wait 1 hour instead of putting in 0.25mg and waiting 24 hours) and wait less but your dosage will be less precise then so it's better to wait.
Once you've waited the required amount of time, make sure all your equipment is sterile including your injection site, filter the extracted Bupe through into your syringe and you're ready to go. Much safer than injecting pills or strips

and it also works out much cheaper since patches are nothing in comparison to the prices of Subutex or Suboxone - though since we can't discuss prices here I can't say how much.
Hope this helps
