Although the gabapentin maybe making you feel funny, this is also true for the percocetts:

Buprenorphine itself binds more strongly to receptors in the brain than do other opioids, making it more difficult for opioids (or opiates) to react when buprenorphine is in the system. The blockade effect also has the result of blocking endogenous endorphins from binding to receptors, which can lead to psychological alterations in mood and mental capacity. This can cause cognitive and memory deficiencies via blockade of the reward system, which is pertinent to memory formation and normal mental function.

My patch has been giving me a headache but no loss in mental/cognitive function... yet... sigh...

J.