Fentanyl Transdermal Patch Application Sites
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| English: 2D structure of fentanyl (Photo credit: Wikipedia) |
Fact or Fiction From Medscape:
Q: Is it true that fentanyl
patches infuse more quickly in patients with very little subcutaneous fat?
A: No. The amount of fentanyl
absorbed is proportional to the surface area of the patch. The absorption rate
does not vary to any clinically significant extent between the chest, abdomen,
and thigh.[5] Fentanyl
is released from the patch into top layers of the skin (stratum corneum and
epidermis), and it accumulates within these layers to form a depot. The drug is
released slowly into the systemic circulation via small blood vessels within the
dermis. Fat tissue should not impair release, as the drug is released directly
from the skin into the blood supply.[2,5]
Furthermore, fentanyl exhibits
wide tissue distribution to the lungs, kidneys, heart, spleen, brain, muscles,
and body fat -- indicating a high extravascular volume of distribution (3-8
L/kg). It takes about 6 days to reach steady-state plasma concentrations after
initiating fentanyl patch therapy.[5]
- Muijsers BBR, Wagstaff AJ. Transdermal fentanyl: an updated review of its pharmacological properties and therapeutic efficacy in chronic cancer pain control. Drugs. 2001;61:2289-2307. Abstract
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