The fentanyl patch is outstanding for pain management, but very potent and I found tolerance developed ultra fast. I went from a 50mcg patch two one 100mcg patch and one 75mcg patch in just two years. I also used the Actiq (fentanyl) lolypop for BT pain which was also excellent, but again my tolerance developed dangerously fast. I also had loads of difficulty keeping the patches on as the med made me sweat quite a bit. to answer your question, it's my opinion that fentanyl is much less constipating than morphine.

It's a great pain med, you just have to be very careful. Have you considered OxyContin? That would be a natural step up from Avinza as oxycodone is about 50% stronger than morphine. You could then use the oxycodone liquid, or tabled for BT medication. I use the concentrated liquid (20mg/1ml) and it works great.

Good Luck!

steve