Fentanyl (Transdermal Patch)

How it works

Fentanyl is a strong mu-opioid receptor agonist; the matrix or reservoir patch delivers it through the skin at a steady rate to maintain continuous plasma concentrations over several days.

Prescribing in practice

• Reserve for opioid-tolerant patients only, as initiating a patch in opioid-naive individuals risks fatal respiratory depression, and never apply to acute pain.
• Heat sources such as fever, hot baths, saunas and electric blankets accelerate absorption and can cause overdose, so warn patients to avoid them.
• Onset and offset are slow: a depot persists in the skin after removal, so monitor for delayed respiratory depression when stopping or switching.

Monitoring

Monitor pain control, sedation level and respiratory rate, especially after initiation, dose change or addition of other central nervous system depressants.

Counselling the patient

• Apply to clean, dry, non-irritated, hairless skin and rotate sites; do not cut the patch.
• Keep used and unused patches away from children and pets, and fold used patches in half before safe disposal as residual drug can be fatal.
• Avoid heat over the patch and report excessive drowsiness or slow breathing.

Evidence & guidelines

MHRA safety communications highlight risks of accidental exposure, heat-related overdose and use in opioid-naive patients, reinforcing the cautions in current prescribing references.