Any narcotic should, if possible, be slowly tapered as physical withdrawal is quite unpleasant. I did a fast taper
that was not supervised by my doctor and it was less than ideal. Fentanyl
can be a bit harder than Percocet, Vicodin, etc. Drinking lots of water is essential as it is really easy to get dehydrated. You can taper from the Fentanyl down and then cross over to a different immediate release narcotic and then taper down from that.
Are you taking anything else?