Are you taking this to have "fun"? or taking it to get pain relief? TBH 12mcg/hour is a pretty low dose for someone with a tolerance (imo). When im a work I typically give my patients 100mcg of fentanyl straight up via IV (which last about an hour). Most of the time, these people don't have an opiate tolerance and they have no problems with it. Note, this is typically for trauma-related problems, Ie. a fractured extremity, but they still have no respiratory type problems.
Obviously, consult your doctor, if this is for pain management. If this is to have "fun", fentanyl's high sucks...compared to hydrocodone. Not much euphoria at all (once again, jmo). I've IV'd pharma grade fentanyl and was EXTREMELY disappointed.
Be safe.