Sun17October0644AM 9

Are the following true of fentanyl transdermal patches?

True / False

Has increased elimination when administered with CYP3A4 inhibitors Correct

They are available only in matrix form Correct

The depot drug has an elimination half life of up to 22 hours after patch removal Correct

Delivers more drug with exposure to heat Correct

Forms a depot within skin layers Correct

Explanation

Transdermal delivery of fentanyl is licensed for chronic and acute pain. It is available as matrix with a rate-controlling membrane (Matrifen) or reservoir patch as well as an iontophoretic transdermal system (ITS) for management of acute pain. The fentanyl ITS is the only transdermal opioid that has a role in the management of acute pain.

Each patch is designed to maintain a constant plasma fentanyl concentration over a 72 hour application with maximum plasma concentrations between 12 and 24 hours. The elimination half life is 13-22 hours.

Exposure to a heat source or an increase in body temperature can increase fentanyl delivery by up to one third. Blood flow and anatomical site of application does not affect the rate of drug delivery.

After application of the patch, a depot of fentanyl forms within skin layers and this accounts for delays in reaching maximal plasma concentration and in elimination following patch removal. Owing to the slow increase in initial fentanyl plasma concentrations, other analgesics may be required during the initial period.

Elimination can be delayed by the co-administration of CYP3A4 inhibitors, for example, ketoconazole, clarithromycin, verapamil, diltiazem and amiodarone.

Reference:

Medicines and Healthcare Products Regulatory Agency (MHRA). https://www.gov.uk/drug-safety-update/serious-and-fatal-overdose-of-fentanyl-patches

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