"very effective for pain. have been pain meds for 11 yrs. tried many others ie. hydrocodone, morphine, percocet, oxymorphone, several others, but nothing worked like fentanyl. however, i have had some serious side effects. first i froze at 78 degrees inside our home in southwest florida. then my left eye started getting really hazy. i thought my glasses were filthy. by the way it&#039;s still hazy after going through almost four months of withdrawal.  then my right leg felt like dead weight at night. my left leg felt like it was wrapped with a very tight sock from below the knee to my ankle. i felt like i was going to vomit any minute, my mouth started to get watery. my gut hurt like anything. "