Fentanyl Transdermal Patch

PHARMACOLOGY

A strong opioid analgesic which produces its effects predominantly via agonist actions at the mu opioid receptor. The transdermal patches deliver a steady hourly dose of fentanyl by utilizing a rate-limiting membrane and the ‘time to peak plasma concentration’ can be up to 48h when first applied. Therefore, they should only be used in the management of chronic, moderate to severe pain requiring around-the-clock opioid therapy after the patient’s opioid requirements have been ascertained. They can be particularly useful in situations where the patient cannot swallow. They are thought to be less constipating than morphine. Fentanyl is less likely than morphine to cause adverse effects in renal impairment.

DOSING

The patient’s opioid requirements should have been previously stabilized by titrating a shorter acting opioid formulation. The strength of the patch to be used should be then be determined on this basis of an equianalgesic chart specifically for fentanyl transdermal patch (see example of one in Equianalgesic Tables). A minority of patients may need to change the patch every 48 hours.

PITFALLS/CONCERNS

It is not recommended to attempt treat uncontrolled or acute pain with fentanyl transdermal patches.

  • The patches, when removed, still contain active medication and should be disposed of as per manufacturers instruction. If left lying around they may be a danger to children
  • See manufacturer’s recommendations or Equianalgesic Tables for conversion to and from morphine

UNWANTED EFFECTS

  • Pruritus
  • Sweating
  • Nausea
  • Vomiting
  • Dry mouth
  • Confusion
  • Dizziness
  • Sedation
  • Urinary retention
  • Constipation

NOTE

This information is drawn from a number of sources (see below). The reader is encouraged to access these and other relevant literature for more detail. As always, sound clinical judgment should be used in individual clinical cases. In particular, it should be remembered that there may be significant variation in the pharmokinetics of a drug resulting from a number of factors, including the individual patient’s metabolism/disease status and how the medication has been formulated.

SOURCES/REFERENCES

  1. Brunton LL, Lazo JS, Parker KL, editors. Goodman and Gilman’s: the pharmacological basis of therapeutics. 11th ed. McGraw-Hill Professional; 2006.
  2. Twycross R, Wilcock A. Palliative care formulary. 3rd ed. Radcliffe Medical Press Ltd; 2008.
  3. Repchinsky C, editor. Compendium of pharmaceuticals and specialties (CPS): The Canadian drug reference for health professionals. 44th ed. Canadian Pharmacists Association; 2009.
  4. Goldman A, Hain R, Liben S. Oxford textbook of palliative care for children. 1st ed. Oxford University Press; 2006.
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