Fentanyl patches: how they work and how to use them safely

The NHS describes fentanyl as a strong opioid painkiller used for severe pain, for example during or after an operation or a serious injury, or pain from cancer, and for other long-term pain when weaker painkillers have stopped working. The patch form is slow-release: the medicine moves gradually through the skin and keeps pain controlled for longer periods. Some patches keep working for a while after they are removed because fentanyl is stored under the skin.

Patches are not for short-lived pain. Tablets, lozenges, nasal sprays or injections work faster and are used for pain expected to last a short time, and a doctor may prescribe one of those alongside a patch for sudden flare-ups that break through.

Most adults can use fentanyl, and some patches can be used by children aged 2 and over, though young children and older people are more likely to get side effects. The central point in the NHS information is that patches are usually used only after you have been taking other strong opioids, because the prescriber needs to match the dose to your existing opioid intake to lower the risk of overdose.

Tell your prescriber if you are not already taking regular strong opioids, have had an allergic reaction to fentanyl, have breathing problems such as asthma, are addicted to alcohol or drink heavily, have a head injury, have a condition causing fits, or have other relevant conditions.

Always follow the leaflet in your pack. The NHS describes the principles below, and says doses are different for everyone, so it never lists a single right strength.

• Apply to clean, dry, flat, undamaged skin that is easy to reach, such as the upper chest or upper arm; trim, rather than shave, very hairy areas. Do not touch the sticky side.

• Press the patch down for at least 30 seconds, especially the edges. Do not cut it and do not cover it with a dressing or tape.

• Change it at the same time of day every 3 days, using a different area of skin each time. Showers and swimming are fine, but check it is still stuck down afterwards.

• If a patch falls off, put a new one on a different area, note the date and time, and change it again after 3 days. If you are very late changing a patch, speak to your doctor before applying a new one.

• Never let a patch stick to anyone else, particularly a child, and never pass a patch on to another person.

Heat is the hazard people do not expect. Long hot baths, saunas, electric blankets, hot water bottles, heat pads and sunbathing can raise the amount of fentanyl absorbed, so do not place a heat pad on or near the patch even to ease stomach pain.

Used patches still contain medicine. Fold the patch in half so the sticky sides stick together, put it back in its packet and take it to a pharmacist to be destroyed. Keep all fentanyl out of reach of children and vulnerable adults. If a patch sticks to someone it was not prescribed for, remove it straight away and get medical help; if a patch is swallowed, call 999.

More than 1 in 100 people get constipation (a laxative is likely to be needed), nausea or vomiting, stomach pain, sleepiness or tiredness, dizziness or vertigo, confusion, headaches, or itching and rashes. Sleepiness and headaches often ease within a week or two. Higher doses make side effects more likely.

Serious effects, in fewer than 1 in 100 people, include unexplained muscle stiffness and symptoms of low blood pressure, for which the NHS says to call a doctor or 111 and remove the patch if you are wearing one. Difficulty breathing, short shallow breathing or a fit needs 999. Taking more than prescribed, even without symptoms, also calls for emergency help.

Tell your doctor if you take medicines for sleep, high blood pressure, irregular heartbeat, sickness, allergy symptoms, mental health problems, anxiety, infections including HIV, or seizures. It is safe with paracetamol, ibuprofen or aspirin, but codeine-containing products such as co-codamol, Nurofen Plus and Solpadeine should not be used with it. Grapefruit juice can raise fentanyl levels, so it is best avoided, and alcohol should be avoided when starting because it increases sleepiness.

In pregnancy it may occasionally be used for severe or hard-to-treat pain, but babies exposed late in pregnancy may have withdrawal such as drowsiness. It can be used while breastfeeding in low doses for a short time, without stopping breastfeeding suddenly. If you have used it for more than a few weeks, do not stop without your doctor, who reduces the patch strength gradually and may switch you to morphine to taper more slowly.