Nucynta
"My Pain mgt. doctor switched me from Demerol to Nucynta for break-through pain of chronic migraines.  Surprisingly, I found it to be effective, but I noticed from the start that it greatly diminished my language skills:  reading, writing, and speaking.  As per doctor's orders I stayed in bed while under the effects of Nucynta so this weird side effect didn't cause me any issues.

     Until...After using it for 15 months, I found my language skills to be extremely loopy, creating comments from friends and neighbors, DAYS after taking Nucynta. That scared me and my doctor immediately took me off this medicine when I finally advised her of the language problem it presented.  I could be reading a sentence and forget a word's meaning."