Fentanyl is a potent opioid that interacts with mu receptors in the brain, spinal cord, and other tissues.
Fentanyl is between 100 and 150 times more potent than morphine on a mg. per mg. basis.
It is highly suited for transdermal delivery based on
Transdermal preparations of fentanyl are available in patches of various sizes. It is currently marketed under the trade name Durogesic DTrans.
The 12 micrograms per hour patch is licensed to facilitate titration between doses of 25 to 50 to 75 microgram per hour. Currently the ‘12’ patch is not licensed for initiation of therapy.
Durogesic DTrans patches release fentanyl slowly into the skin and underlying tissues from its solid drug- in-adhesive matrix.
Following initial application, the skin under the system absorbs fentanyl and a depot of fentanyl concentrates in the upper skin layers but is rapidly absorbed into bodily adipose tissue.
Once the lipid stores have been saturated the plasma level starts to increase gradually until it levels off at 12-24 hours (the time taken for the older reservoir patch was 36-48 hours).
Onset of analgesia is reached in approximately 6-12 hours and analgesic effect, lasts for approximately 72 hours.
Durogesic DTrans has an average elimination half- life of 17 hours.
This means that after removal of patch, serum fentanyl levels decline slowly with on average a 50% reduction in 17 hours (range 13-22 hrs)