Can anyone help with the carbon footprint of fentanyl and butrans patches please?

Hello! 

We are evaluating the carbon footprint of our team's structured medication reviews for a large cohort of frail people living in care homes (we see about 1500 residents a year) and eventually hoping to come up with a guide for GPs and geriatricians on deprescribing including clinical rationale, carbon impact, and financial cost. We have used the Yewmaker tool so far to calculate carbon impact, which is fantastic, but there are a few commonly deprescribed medications we are missing.

In particular does anyone have the carbon footprint of fentanyl/butrans patches?

Can I check that we aren't trying to re-invent the wheel? (has anyone else started this work?)

And finally - is anyone interested in joining us?

Thanks so much!