Denpax, a new brand of fentanyl transdermal matrix patch is available on the PBS from 1 August 2011.

The Pharmaceutical Benefits Advisory Committee recommended listing Denpax1 on a cost-minimisation basis, as it is equivalent in efficacy and cost compared with the existing brand, Durogesic.2

Both brands of fentanyl patch are bioequivalent

The new brand of fentanyl patch (Denpax) is bioequivalent to the existing brand (Durogesic). Equivalent strengths of both brands deliver equivalent amounts of fentanyl per hour over the 72-hour dose period and may be substituted for each other. Denpax patches contain a smaller amount of fentanyl because they have a smaller surface area than Durogesic patches (see Table 1). However, the strengths (hourly rates) are interchangeable and there is no expected difference in efficacy. Provided the patches are replaced after 72 hours, as per dose recommendations, the amount of fentanyl delivered to the patient remains the same.

Table 1.
Fentanyl patch characteristics

Fentanyl delivery rate Fentanyl content Patch surface area
Denpax Durogesic Denpax Durogesic
12 micrograms/hour 1.28 mg 2.1 mg 3.13 cm2 5.25 cm2
25 micrograms/hour 2.55 mg 4.2 mg 6.25 cm2 10.5 cm2
50 micrograms/hour 5.10 mg 8.4 mg 12.50 cm2 21.0 cm2
75 micrograms/hour 7.65 mg 12.6 mg 18.75 cm2 31.5 cm2
100 micrograms/hour 10.20 mg 16.8 mg 25.00 cm2 42.0 cm2

Each fentanyl patch must be worn continuously for 72 hours then replaced. The dose may be adjusted at 3-day intervals after the initial application to achieve the most appropriate dose to balance effective analgesia with tolerability. For more information refer to NPS News 69 and NPS Prescribing Practice Review 51. Reserve fentanyl patches for opioid-tolerant patients.

Fentanyl patches are PBS subsidised for chronic, severe disabling pain not responding to non-narcotic analgesics. Hypoventilation (respiratory depression) may occur at any time during use and may be fatal. Fentanyl patches are recommended for patients with demonstrated opioid tolerance, and treatment initiation with transdermal fentanyl is guided by current opioid use (see NPS News 69).

Fentanyl patches are not recommended in opioid-naïve people with non-cancer pain. If fentanyl patches are used in opioid-naïve patients with cancer pain, start with low doses of immediate-release opioids to establish an equi-analgesic dose before switching to a transdermal delivery system (refer to the manufacturer’s product information). Never initiate fentanyl patches in doses >25 micrograms/hour in opioid-naïve patients.

Denpax and Durogesic patches are different in appearance

Denpax and Durogesic patches differ in size and print colour. Advise patients of the different appearance if the brand of fentanyl patches is changed.

Denpax are rectangular-shaped transparent patches. Each strength is imprinted with the dose details in white text. For example, the 12 microgram/hour Denpax patch is labelled: ‘Fentanyl 12 μg/hr’ in white.

Durogesic are rectangular-shaped transparent patches. Each strength patch is identified with the brand name and dose, with different-coloured wording for each strength. For example, the 12 microgram/hour Durogesic patch is labelled: ‘Durogesic 12 μg fentanyl/h’ in orange.

Refer to the Denpax and Durogesic consumer medicine information for a description of each product.

Information for patients

Patients and carers may not be familiar with transdermal patches. Provide the following advice about using and disposing of fentanyl patches:

  • stop using one brand of patches when switching to another, and take any unused patches to the pharmacy for safe disposal
  • never wear more than the one brand of fentanyl patch at one time
  • do not expose the patch application site to heat, as this can increase fentanyl absorption, with serious consequences
  • do not cut or divide fentanyl patches
  • keep a written record of patch application sites and apply a new patch to a different skin site after removal of the previous patch
  • used patches still contain some fentanyl. Fold the used patch in half, so that the adhesive layer sticks together, before disposing of it safely out of the reach of children
  • read the Consumer Medicine Information before applying the patch.


  1. Alphapharm Pty Ltd. Denpax product information. May 2011.
  2. Janssen-Cilag Ltd. Durogesic product information. March 2011.