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Fentanyl is a very potent opioid that, as a pain patch, is released evenly through the skin over three days. It is intended for people with severe chronic pain who are already used to opioids. Because the active ingredient comes from a depot in the skin, it reacts sensitively to heat, keeps working long after the patch has been removed — and is life-threatening to children even in small amounts.
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A fentanyl patch contains an amount of active ingredient that can be fatal to children — even a used one, because after three days a considerable part of the active ingredient is still inside it. The manufacturers, in agreement with the BfArM (German Federal Institute for Drugs and Medical Devices), have therefore issued several warnings in Rote-Hand-Briefe (red hand letters, safety alerts to healthcare professionals): in 2014 after deaths in children who had come into contact with patches, and in 2023 with a new warning on the pack and pouch: “Accidental use or ingestion can be fatal”.⁴,⁵
What applies in your municipality is explained in the guide Disposing of medications.
Fentanyl is broken down in the liver almost entirely via the enzyme CYP3A4. Medicines that slow down or speed up this enzyme change the fentanyl level — in some cases considerably. On top of this come all medicines that also have a sedating effect.¹
| Combination | Consequence | What to do |
|---|---|---|
| Benzodiazepines such as diazepam or lorazepam, sleeping pills such as zolpidem | Sedation, respiratory depression, coma, death possible | According to the SmPC, only if there is no alternative — lowest dose, shortest duration, close observation |
| Pregabalin, gabapentin, muscle relaxants, sedating antihistamines, other opioids | Increased sedation and respiratory depression | Combine only deliberately, limit the dose, watch for tiredness and breathing |
| Alcohol | Increased sedation and respiratory depression | Avoid; see Medications and alcohol |
| CYP3A4 inhibitors, e.g. clarithromycin, erythromycin, fluconazole, itraconazole, verapamil, diltiazem, amiodarone, ritonavir | Fentanyl level rises; severe respiratory depression has been described, including one death with a moderately strong inhibitor | According to the SmPC, not recommended except under close monitoring; reduce the dose or pause if necessary |
| CYP3A4 inducers, e.g. carbamazepine, phenytoin, phenobarbital, rifampicin | Fentanyl level falls, pain increases — and the level rises again when the inducer is stopped | When starting and stopping the co-medication, monitor the dose and effect closely |
| Serotonergic medicines, e.g. sertraline, citalopram, venlafaxine, duloxetine | Serotonin syndrome possible (restlessness, tremor, fever, muscle twitching, diarrhoea) | Caution, especially when starting and changing the dose; report warning signs immediately |
| MAO inhibitors | Severe, unpredictable reactions | Not recommended; fentanyl no earlier than 14 days after the end of an MAO inhibitor |
| Buprenorphine, nalbuphine, pentazocine | Weaken the effect of fentanyl, can trigger withdrawal | According to the SmPC, not recommended |
Many CYP3A4 inhibitors are not exotic medicines but everyday ones: a macrolide antibiotic for bronchitis, an antifungal, a heart medicine. They are often prescribed by a different practice from the one that prescribes the patch. According to the SmPC, after stopping an inhibitor you should generally wait two days before applying the first patch, and longer with long-acting inhibitors such as amiodarone; conversely, at least one week after the last patch before starting an inhibitor.¹ In everyday life this is rarely practicable — which makes it all the more important that every prescribing practice knows about the patch. So add it to your digital medication plan and check new medicines with the interaction check. The basics are in the guide Drug interactions.
Anyone who uses an opioid for weeks or months is physically used to it. According to the SmPC, a fentanyl patch should therefore never be stopped abruptly; reducing too quickly can trigger severe withdrawal symptoms and uncontrolled pain. Tapering off a high dose can take weeks to months.¹
According to the SmPC, fentanyl may only be used during pregnancy if it is clearly necessary. After longer use, withdrawal symptoms in the newborn have been described. Fentanyl passes into breast milk; you should not breastfeed during treatment and for at least 72 hours after removing the patch.¹ Independent advice on your individual situation is available from Embryotox.⁶ Plan a pregnancy early with your practice and also read Medications during pregnancy.
In older age, fentanyl is broken down more slowly, and sensitivity to tiredness, confusion and falls is higher. In care homes and with home care services, the patch — with its application date and site — belongs in every handover; forgotten or double patches are a known risk. Tips on this in the guide Medications in care homes.
Before any operation, anaesthetic or examination under sedation, say that you are wearing a fentanyl patch. Whether it stays on, is changed or is replaced by a different pain treatment is decided by the treatment team. See Medications before surgery.
According to the SmPC, fentanyl can impair your ability to drive and use machines.¹ You should not drive during the adjustment phase, after any change in dose, when you are tired or in combination with alcohol or sleeping pills. Whether you can drive again on a stable dose is an individual decision to discuss with your practice. More under Medications and driving.
For travel to other Schengen states, you need a certificate under Article 75 of the Convention implementing the Schengen Agreement for medically prescribed narcotics; it is filled in by the practice and certified by the competent authority of the federal state, and is valid for a maximum of 30 days. Other countries have their own rules, which you should ask the embassy of your destination country about in good time.⁷ Also bear in mind heat, sunbathing and saunas at your holiday destination. More tips in the guide Medications when travelling.
Not on your own. According to the SmPC, an earlier change is only intended for the very first patch, if the effect is not sufficient in the initial phase. If your pain regularly increases before the change, that is an important finding for your practice: you may need a different strength, better as-needed medication or a different changing rhythm — but that is for the treatment team to decide. Until your appointment, note exactly when the pain rises and how severe it is. A record covering two or three patch changes says more than an impression.
First check the causes: was the skin pre-treated with soap or cream? Is it really dry? Was the patch pressed on firmly for 30 seconds? Some package leaflets allow the edges to be secured additionally with a suitable plaster or adhesive film — ask your pharmacy what applies to your product. Never use a heat patch for this and never stick a second fentanyl patch over it. If the patch comes off completely, the rule from section 4 applies: a new patch of the same strength on a different site, and let your practice know.
As a rule, not on your own — but you should not ignore it. Fever increases the absorption of fentanyl, which is why the SmPC requires close monitoring and, if necessary, a dose adjustment. Call your practice and say explicitly “fentanyl patch and fever”. Ask someone to check on you over the next few hours, especially at night. If you become unusually sleepy, breathe slowly or are difficult to wake, the rule is: patch off and call 112.
The interaction check tests every new medicine against your whole list — including the patch nobody can see.
