A question on fentanyl dosage.

[JasNod]

I've already posted this in the OD forum, but I'm not getting much help, so I was thinking this might be the more appropriate place for my question.

If I did the math correct, and I did it many times, a 1cm x 1cm square of a 100mcg/hr (16.8 mg) duragesic fentanyl patch, taken bucally, should equal about 40mg of oxycodone, taken orally. I understand that different drugs will be metabolized more/less effectively in different people, and that tolerance has to be accounted for, but am I in the ballpark? It feels like a smaller dose than that. I'm not getting a great buzz going, however it is a wonderful drug for pain relief.

For future reference, how should I go about posting the same thread in a different forum? Do I delete the original?

 

[effie]

JasNod, the best thing is to contact a moderator and ask them to move the thread. Would you like the one in OD closed or would you like this one closed and the OD thread brought over? Dosage questions generally belong in BDD but there is some overlap.

I would need to sit down and do the maths myself..

One problem is there is no guarantee that the fentanyl is distributed evenly across the patch - one piece might have a higher dose than another. Another issue is the ROA - bioavailability via this route is variable, and the fentanyl won't be released all at once (although a lot faster than transdermal). For these reasons dosing fentanyl this way can be pretty risky and I would not recommend trying bigger and bigger pieces - it's very easy to tip over into overdose territory especially given the variables I mentioned. How long have you left the patch in your cheek for?

 

[JasNod]

I would say close the other one, thanks. I'm aware that buccally is around 50% bioavailability. I was under the impression that these patches were pretty reliably even, I may have been mistaken. In my experience the same sized patch feels he same though. Also, I'm not getting that fucked up on these, I'm mostly using them for pain, but transdermal seems a bit risky to me because of the whole build up under the skin thing. If I want to get a nice high going, I've just been getting it started with fentanyl and finishing it off with a weaker opiate, just in case.

The math I used went like this (this is by memory though, but I believe the numbers are right): I started wih he assumption that the patch was evenly distributed, and contained 16.8mg, as it said on the package. The patch is 42 cm squared, so I divided by 42 and ended up with 400 mcg each cm squared. I used a converter that seemed reliable after checking wih a few conversions I was familiar wih, and found that this dose taken IV, is roughly equal to 80 mg of oxycodone taken orally. I cut this number in half due to the estimated 50% bioavailability taken orally, and was left with 40 mg of oxycodone. Does this sound like a good approximation to you?

 

[effie]

It depends which patch you have, some are more consistent than others. Transdermal can be dodgy indeed, given how long it takes to reach peak plasma levels and with the subcutaneous deposition as you say.. (I remember discussing this in OD). It's safe for analgesia when you have titrated up to fentanyl but it's dangerous for someone trying to get high. As far as I can see your maths does look right but I'm really tired so not thinking 100% straight right now! Fentanyl maths scares me, when you're dealing with something as potent as that it is vital that you don't make a mistake..

I wonder if maybe you are getting reduced effects as it still takes some time to reach peak plasma levels? Alternatively fentanyl might not be recreational for you - it isn't for some people, and the fact that you are getting good analgesia but not much buzz suggests this may be the case. Either way I would be very cautious about increasing my dose as you could easily tip over into an overdose.

 

[JasNod]

Yea, unfortunately I'm well aware of the problem of it's potency... However, I personally have never overdosed on fentanyl. Actually, I've never even attempted to nod on fentanyl. It feels to me like it kicks in about 20 minutes, but doesn't peak until maybe a little over an hour. Are your experiences with this drug similar? Thanks a lot for your answer and concern. I try to be careful, but sometimes... you just want that nod.