pain
"Excellent!  I suffered from inadequately controlled back pain for decades.  Finally when several sleep studies confirmed that at least part of my daytime sleepiness was due to pain issues, I was put on Fentanyl patches.  While we did have to experiment with dosing the back pain has been well controlled for decades with NO side effects!  It did not work well for my joint pain, but I have other treatment options that are effective.  While I have had a recent increase in breakthrough pain, it is likely because my sleep disorder (unrelated to pain) has exacerbated considerably and I've been unable to change my patches on schedule."