The Fentanyl is indicated for long term pain relief and takes an initial 3 days to reach therapeutic levels in the blood. Morphine is a fast acting opiate for breakthrough pain. Those were what worked for me at that phase in treatment. Based on how much morphine I was adding, they would titrate the amount and add to my Fentanyl dose. I was taking Dilaudid, when I was in the hospital, and it was very effective and fast acting (although it was IV and not oral. Speak with your pain management team.