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Fentanyl patches to be available without Special Authority in 2011

From 1 February 2011, primary care clinicians will be able to prescribe fentanyl patches, fully funded, without the need for Special Authority.

Mylan Fentanyl Patch (previously known as Duropatch) will be available in 12.5 mcg, 25 mcg, 50 mcg, 75 mcg and 100 mcg strength matrix-style, transdermal patches. The currently funded brand of fentanyl patches (Durogesic) will remain available via Special Authority approval until 1 February 2011. After this time, Durogesic will only remain funded for patients who have an existing approval (until 31 July 2011).

Timeline of events:

1 February 2011 Mylan Fentanyl Patch fully funded, without the need for Special Authority
Durogesic remains fully funded, via Special Authority, but no new Special Authority approvals granted
1 August 2011 Durogesic no longer funded and delisted from the Pharmaceutical Schedule
Suggested course of action for prescribers in 2011:
Up to 1 February Continue to support existing patients taking Durogesic and apply for Special Authority for Durogesic for new patients who require fentanyl
1 February - 1 July Continue to support existing patients taking Durogesic and prescribe Mylan Fentanyl Patches for new patients who require fentanyl
1 July - 31 July If any patients still remain on Durogesic, begin a transition process to Mylan Fentanyl Patches
1 August All patients who require fentanyl should be prescribed Mylan Fentanyl Patches

Switching brands of fentanyl

Mylan Fentanyl Patch is regarded by Medsafe as being bioequivalent to Durogesic. Therefore it is expected that for most patients, changing brands would not require a dose adjustment. However, it is anticipated that the transition period will mean that changing brands should not be required in most cases. New patients should be started on Mylan Fentanyl Patch and most patients initiated on Durogesic before 1 February 2011 should have completed their treatment within the sixth month “grandparenting” period when both brands are available.

If patients do need to change brands, they should be switched to the equivalent dose of the new brand and their clinical response monitored closely. If problems do arise, dose adjustment may be necessary. If overdose symptoms occur, consider reducing to a lower dose. If pain is not managed, consider switching to a higher dose or adding a “breakthrough” dose of morphine.

Who should fentanyl be considered for?

Fentanyl patches may be useful for people with stable, persistent, chronic pain conditions, who are unable to take oral morphine or cannot tolerate morphine-associated adverse effects. Fentanyl may also be a more suitable option than morphine for patients with renal failure.

Fentanyl patches are not an appropriate choice for rapid pain management and should not be used in opioid-naïve patients with non-cancer related pain. Care should also be taken if fentanyl patches are prescribed to elderly and debilitated patients in whom the effects may be potentiated.1

Dosing for fentanyl patches

Start with the lowest possible dose, based on the patient’s opioid history and pain condition. Calculate the patient’s 24 hour morphine (or morphine equivalent) dose and convert this to the appropriate fentanyl patch dose (Table 1). Patches are applied for a 72 hour period.

Table 1: Recommended fentanyl dose based on daily oral morphine dose2
Oral 24-hour morphine dose Fentanyl patch dose
60 - 134 mg 25 mcg/hour
135 - 224 mg 50 mcg/hour
225 - 314 mg 75 mcg/hour
315 - 404 mg 100 mcg/hour
405 - 494 mg 125 mcg/hour
495 - 584 mg 150 mcg/hour
585 - 674 mg 175 mcg/hour
675 - 764 mg 200 mcg/hour
765 - 854 mg 225 mcg/hour
855 - 944 mg 250 mcg/hour
945 - 1034 mg 275 mcg/hour
1035 - 1124 mg 300 mcg/hour

N.B. This table is based on conversion doses for Durogesic.
As Mylan Fentanyl Patches are bioequivalent to Durogesic, it is assumed that the same conversion doses would apply.

If the patient is taking a medicine other than morphine, calculate the total daily dose and multiply by the following factors to get the morphine equivalent dose: codeine 0.1, dihydrocodeine 0.1, tramadol 0.2, oxycodone 1.5-2.0 and methadone 5-20 (seek specialist advice).

Remember the “ABC” of pain management:

  • Consider prescribing an Antiemetic for nausea
  • Calculate a Breakthrough dose of morphine, based on one sixth of the morphine equivalent daily dose
  • Fentanyl may be less Constipating in some patients than morphine, so laxative dose may need to be reduced

Adverse effects of fentanyl

High doses of fentanyl can cause respiratory depression. Local reactions from fentanyl patches may include rash, erythema and itching.1

Medicine interactions with fentanyl

Other central nervous system depressants, including opioids, sedatives, hypnotics, muscle relaxants, sedating antihistamines and alcohol, can potentiate the effect of fentanyl.

Concurrent use of CYP3A4 inhibitor medicines, such as erythromycin, ketoconazole, verapamil, diltiazem or amiodarone, can result in an increase in plasma concentrations of fentanyl and should be avoided.1

Fentanyl can interact with monoamine oxidase inhibitors (MAOI), therefore should not be used within 14 days after discontinuation of treatment with a MAOI.

Stopping fentanyl

The effects of fentanyl, including adverse effects, may persist for 24 hours after removal of the patch.1 Ideally, patients should be titrated to a lower dose, before stopping fentanyl.

Practical tips

  • Apply patches to non-hairy skin on the torso or upper arms (it is not necessary to shave the area)
  • Do not cut patches to modify the dose
  • Avoid localised heat being applied to the patch as this may increase blood fentanyl levels
  • Fever and vigorous physical activity can also increase transdermal absorption of fentanyl
  • If patches lose adherence they can be covered with a waterproof dressing
  • Remove the old patch before applying the new patch to a different skin site
  • Dispose of used patches safely as they can still contain significant amounts of fentanyl

For further information about the use of fentanyl patches and pain management, see BPJ 16 (Sept, 2008).

References

  1. Sweetman SC (editor). Martindale: The Complete Drug Reference [online]. London: Pharmaceutical Press; 2010. Available from: www.medicinescomplete.com (Accessed Nov, 2010).
  2. Janssen-Cilag (New Zealand) Ltd. Durogesic medicine safety datasheet. 2010. Available from: www.medsafe.govt.nz. (Accessed Nov, 2010).