Dr. Mark Prausnitz testified for the plaintiffs in a Duragesic lawsuit about the various ways the fentanyl patch can malfunction and kill the wearer. 

I’ve attached his entire eleven page report in PDF format below, but here’s one of the major conclusions he came to:

A lethal fentanyl dose may be achieved individually or by a combination of the effects of (i), loss of the rate-controlling membrane (ii) increased skin permeability, (iii) increased skin area contacting fenantyl gel and (iv) supersaturation of the fentanyl gel formulation.

This leads me to believe that the Duragesic fentanyl patches are defectively designed.  Certainly, I’d only use a Duragesic patch if I would literally rather die than suffer from whatever pain I’m in.  Especially since I don’t know how permeable my skin is.  Skin permeability plays a part in determining how much fentanyl you absorb from the patch.  If you have superpermeable skin, you’re more likely to absorb a lethal amount of fentanyl.  The more I learn about the patch from reading documents produced in litigation, the more wary I become of Duragesic and fentanyl patches.

Here is Dr. Prausnitz’ expert report from this lawsuit in PDF format.