Morphine patch: transdermal opioids for chronic pain
The term morphine patch is in common usage but pharmacologically not entirely accurate. Morphine itself is poorly absorbed through the skin, which is why classic morphine preparations come as tablets, solutions or injections. When patients refer to a morphine patch they usually mean fentanyl patches (Durogesic SMAT, Matrifen, generics) or buprenorphine patches (Norspan, Transtec, generics). Both are opioids applied as transdermal therapeutic systems (TTS).
Transdermal opioids have a firm place in the therapy of chronic pain, especially tumour-related pain. They allow constant drug delivery over several days, avoid the gastrointestinal problems of oral preparations and are an option when swallowing difficulties or absorption disorders are present.
Mechanism of action
Both fentanyl and buprenorphine are opioids that bind to opioid receptors, primarily the μ receptor (mu receptor). Activation dampens pain transmission in the spinal cord, alters pain processing in the CNS and modulates the emotional appraisal of pain.
- Fentanyl: pure μ agonist, about 80 to 100 times stronger than morphine in equianalgesic dosing; lipophilic, hence well effective transdermally
- Buprenorphine: partial μ agonist and κ antagonist, about 25 to 50 times stronger than morphine; ceiling effect at higher doses (ceiling for respiratory depression, not for analgesia); longer half-life
With transdermal application the opioid is released continuously from a reservoir or matrix into the skin and absorbed via microcapillaries into the circulation. A stable plasma level is only reached after 12 to 24 hours, which is why short-acting on-demand medication is often combined in the initial phase.
Indications
- Chronic tumour pain: main indication, especially with stable pain pattern and even requirement
- Chronic non-tumour pain: on strict indication when other therapies have been exhausted and a clear benefit exists
- Not suitable for postoperative pain therapy: as the effect sets in only after hours and is poorly controllable
- Patients with swallowing difficulties, gastrointestinal absorption disorders or compliance issues: hard to manage with oral therapy
Important: patches are not acute medication. Short-acting on-demand opioids must be prescribed for breakthrough pain.
Dosing and administration
Fentanyl patches: available in 12, 25, 50, 75 and 100 µg per hour, change every 72 hours. Some preparations allow change every 84 hours.
Buprenorphine patches: low-dose patches (Norspan) at 5, 10, 20 µg per hour, change every 7 days. Higher-dose patches (Transtec) at 35, 52.5, 70 µg per hour, change every 96 hours.
Application:
- Apply to dry, hairless, intact skin (upper body, upper arm, chest)
- Rotate the application site, do not use the same area too often
- Trim hair if necessary, do not shave
- Do not cut the patch
- Avoid heat sources (heating pads, hot baths, sauna), as these can drastically increase uptake
- Used patches: stick together adhesive side inwards and dispose of safely in the original packaging
Switch from oral therapy: use equivalence tables, plan an overlap phase. Apply the first patch and give the last oral sustained-release tablet in parallel.
Side effects
Very common: nausea (especially at the start of therapy), vomiting, constipation, dry mouth, dizziness, fatigue, headache, sleep disturbance.
Common: confusion, hallucinations, pruritus at the patch site, skin redness, sweating, sexual dysfunction, hormonal effects (hypogonadism, hyperprolactinaemia).
Uncommon: respiratory depression (especially with overdose or combinations), bradycardia, hypotension, urinary retention, allergic skin reactions.
Rare: anaphylaxis, hyperalgesia, seizures, paralytic ileus, severe skin reactions, addiction with tolerance and withdrawal.
Important risks:
- Respiratory depression is the most dangerous complication, life-threatening especially in opioid-naive patients
- Heat massively increases absorption, with risk of overdose
- Patch residues can cause severe poisoning in children or pets if disposed of improperly
- In hyperthermia or sepsis absorption can rise; remove the patch if necessary
Interactions
- Other CNS depressants (benzodiazepines, alcohol, Z drugs, antipsychotics, sedating antihistamines): additive respiratory depression and sedation, caution or avoid combination
- Strong CYP3A4 inhibitors (itraconazole, ketoconazole, HIV protease inhibitors, erythromycin): raised fentanyl levels with dangerous respiratory depression
- Strong CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St John's wort): reduced levels, loss of effect
- MAO inhibitors: risk of serotonin syndrome and circulatory reactions
- Naloxone and naltrexone: reversal of effect with acute withdrawal
- Buprenorphine and pure μ agonists: partial antagonism due to the partial agonist action of buprenorphine
Special considerations
Pregnancy: only on strict indication, since chronic opioid exposure can lead to neonatal withdrawal syndrome.
Breastfeeding: passage into breast milk, individual evaluation depending on the substance.
Older patients: increased sensitivity, risk of falls and confusion. Low starting doses and close observation are recommended.
Contraindications: acute respiratory depression, severe asthma, paralytic ileus, opioid-naive patients in acute pain therapy, severe hepatic impairment.
Addiction potential: fentanyl has a high abuse potential, buprenorphine less so due to the ceiling effect. Safe storage at home is important (protect from children and pets).
Emergency identification: patients on opioid patches should carry a pain card documenting substance, dose and last patch change. In emergency (unconsciousness, respiratory depression) naloxone is used; for buprenorphine higher doses are needed.
End of therapy: do not stop patches abruptly. Since the skin depot continues to release, slow stepwise reduction may be sensible to avoid withdrawal symptoms.
Related substances
- Morphine, classic opioid for strong analgesia
- Oxycodone, orally available strong opioid
- Tapentadol, μ agonist plus noradrenaline reuptake inhibitor
- Morphium patch, alternative spelling with same content
Frequently asked questions
Does a morphine patch really contain morphine?
No. Classic pain patches contain fentanyl or buprenorphine. Morphine itself is not sufficiently absorbed transdermally. In everyday speech, however, the term morphine patch is often used for all opioid patches.
Why must I avoid the sauna with the patch?
Heat increases skin perfusion and thus uptake of the opioid into circulation. Even a hot bath or heating pad can considerably raise plasma levels, with risk of respiratory depression. Sauna, hot baths and heating pads are off-limits during use.
What about breakthrough pain on a patch?
Patches provide baseline coverage but do not address acute pain peaks. A short-acting opioid (drops, sublingual tablet, buccal tablet, nasal spray) is prescribed in addition. If on-demand requirement rises, the baseline dose should be adjusted.
How do I dispose of used patches safely?
Used patches still contain residual drug. Fold them adhesive side inwards and dispose of in the original packaging or household waste. Important: keep out of reach of children and pets, since even a licked or swallowed patch can be life-threatening.
Sources
- BfArM Federal Institute for Drugs and Medical Devices
- EMA European Medicines Agency
- AWMF guideline LONTS and tumour pain
- Gelbe Liste opioid monographs
Legal notice and disclaimer
The information on this page is provided for general information purposes only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. Medicines should only be used after a doctor's prescription or pharmacy supply. All information is based on summaries of product characteristics and accepted scientific sources at the time of writing; the current SmPC of the manufacturer is always decisive. Sanoliste accepts no liability for completeness, timeliness or accuracy. In a medical emergency, dial the emergency number 112.