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You already have transdermal buprenorphine and fentanyl. What exactly is the special place for transdermal oxymorphone. It certainly wasn’t first choice for POH - which spent many years pursuing oxycodone.

To specifically answer your question regarding transdermal TPM-mediated oxymorphone as set against transdermal buprenorphine and fentanyl, the most obvious difference is that (in the United States at least) neither buprenorphine or fentanyl is recommended for opiate-naive patients.

Therefore the potential markets for these two patches are quite limited as compared to an effective oxymorphone patch. Beyond that there are the well publicized difficulties with the Fentanyl patch which also have served to limit its market.

It's true that ocycodone was the first transdermal project taken on they POH, and it is also true that problems were encountered with crystallization within the matrix. This was solved, but I suspect it was solved at the expense of reduced oxycodone concentrations implying a larger patch size.

The oxymorphone option would possibly allow for lower opioid concentrations in the matrix implying a more commercially acceptable patch size. I don't think there is much reason to look deeper for the reason for the change in direction.