Pain Patch.
I've used pain patches before, but never even close to an open wound. It messes with the way the medication is released and normally you should never put a patch on or near even a scratch.
You probably want to check with your doc or at least a pharmacist.
There are many different types of patches from narcotics to NSAIDS. I don't know what surgery you've had but NSAIDS - even those released from a patch - are to be avoided at pretty much all costs if you've had an RnY.
good luck,
amy