Strong opioid
Fentanyl
Fentanyl citrate
Fentanyl is a very potent synthetic opioid, many times stronger than morphine. In the UK it is used as patches for stable, severe long-term pain in people already used to opioids, and in anaesthesia and specialist palliative care.
How this medicine is supplied
Prescription only — specialist use in the UK. Dispensed by us only against a valid prescription from a UK prescriber.
How prescriptions workFentanyl overdose can be fatal within minutes. Call 999 and say that you suspect an opioid overdose. Naloxone reverses opioid overdose and is available free from many UK pharmacies.
What it is used for
- Severe, stable long-term pain in people already taking a strong opioid (patches)
- Breakthrough cancer pain, under specialist supervision
- Anaesthesia and intensive care (hospital only)
How it works
Fentanyl acts on opioid receptors and is roughly 100 times more potent than morphine. A patch releases medicine steadily through the skin over three days, which suits stable pain but makes the dose very difficult to adjust quickly.
Forms available in the UK
- Transdermal patches, changed every 72 hours
- Sublingual tablets and buccal films for breakthrough pain
- Nasal spray
- Injection (hospital only)
Safety information you must know
- Fentanyl patches are only for people who are already opioid-tolerant. Used in someone who is not, they can be fatal.
- Heat dramatically increases how much fentanyl is absorbed. Avoid hot baths, saunas, electric blankets, heat pads and sunbeds, and tell your prescriber if you develop a fever.
- Never cut a patch unless your prescriber has told you to, and never apply more patches than prescribed.
- Fold used patches sticky-side together and return them to a pharmacy. Even used patches contain enough fentanyl to harm a child or pet.
- Counterfeit fentanyl tablets sold online have caused many deaths in the UK. Never take a tablet that did not come from a pharmacy.
- Do not combine with alcohol, benzodiazepines or gabapentinoids.
Common side effects
- Drowsiness and sedation
- Constipation
- Nausea and vomiting
- Skin irritation where the patch is applied
- Confusion
- Slow, shallow breathing — a medical emergency
Interactions to be aware of
- Alcohol and sedatives
- Benzodiazepines
- Gabapentin and pregabalin
- Some antifungals and antibiotics
- MAOI antidepressants
UK legal position
Fentanyl is a Class A controlled drug and a Schedule 2 prescription-only medicine. It is initiated by specialists and is not dispensed to new patients without an existing prescription and clinical review.
Brand names you may see
Brand names are listed for identification only. We do not endorse or supply them.
This page provides general information only and does not constitute medical advice, a prescription or an offer to supply. Doses are decided by your prescriber. If you think you may need this medicine, speak to your GP, an NHS 111 clinician or a specialist pain service. In an emergency, call 999.