Side Effects Of Fentanyl

Like all medicines, fentanyl can cause side effects in some people but many people have no side effects or only minor ones.

You're more likely to get side effects with higher doses of fentanyl.

Common side effects

These common side effects of fentanyl happen in more than 1 in 100 people. There are things you can do to help cope with them:

Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.

Serious side effects

Serious side effects happen in less than 1 in 100 people.

Call a doctor or call 111 now (and remove a patch if you're wearing one) if:

• your muscles feel stiff for no obvious reason
• you feel dizzy, tired or have low energy - these could be a sign of low blood pressure

Call 999 now if:

Do not drive yourself to A&E.

The person you speak to at 999 will give you advice about what to do.

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to fentanyl.

Call 999 now if:

• your lips, mouth, throat or tongue suddenly become swollen
• you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
• your throat feels tight or you're struggling to swallow
• your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
• you suddenly become very confused, drowsy or dizzy
• someone faints and cannot be woken up
• a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

Long-term side effects

Some people with conditions that need long-term pain relief may need to take fentanyl for a long time.

If you need to take it for a long time your body can become used to it (known as tolerance). That means you need higher doses to control your pain over time.

Some people can become more sensitive to pain (hyperalgesia). If this happens, your doctor will reduce your dose gradually to help these symptoms.

It's possible to become addicted to fentanyl. For this reason, your dose will be reviewed to make sure you're only having the amount you need to control your pain.

Your treatment plan may include details of how and when you'll stop fentanyl.

If you're having treatment for cancer pain or other severe pain, your pain control will be carefully monitored. Speak to your doctor if you're worried about tolerance, hyperalgesia or becoming addicted.

Other side effects

These are not all the side effects of fentanyl. For the full list, see the leaflet inside you medicines packet.

Reporting side effects

You can report any suspected side effect using the Yellow Card safety scheme.

Visit the Yellow Card website for more information about reporting side effects.

Sexual Health Advice

• Sexual Health Advice - Introduction and Overview
• The MenB vaccine that helps protect against gonorrhoea
• Sexual Health - Mpox and its dangers for Gay Men
• What happens when you visit an STI Clinic
• Ejaculation issues are common sexual problems in men
• The Male Menopause for men in their late 40s to early 50s
• Help and care if you have been Sexually Assaulted
• Mental health issues and self-harm are common amongst gay men