Morphine: how it is used for severe pain and what to expect

The NHS describes morphine as an opioid painkiller used to treat severe pain, such as pain after an operation, after an injury, from cancer, and during end of life (palliative) care. It is not a first-step painkiller: it is chosen when the pain is severe and a prescriber has judged that the benefit outweighs the risks.

Anyone who has taken it for a long time and finds that it is no longer controlling their pain, or who has pain between doses, should tell their doctor rather than increasing the amount themselves.

Morphine usually comes as tablets, capsules or a liquid (oral solution) that you swallow. It can also be given by injection or through a thin tube into a vein, but that is generally done in a hospital or hospice. Some tablets are taken differently, for instance dissolving on the tongue, and the brand names above include both short-acting and prolonged-release types.

The amount and the length of treatment depend on the reason and the type, so follow your prescriber and the leaflet. Swallow tablets or capsules whole with a glass of water and use the syringe or cup that comes with a liquid so that each dose is measured accurately.

The NHS lists constipation, nausea or vomiting, sleepiness, dizziness, confusion, headaches and itchy skin or rash as common. If you feel dizzy, sleepy or confused, do not drive, cycle or use machinery until it has passed. Speak to a pharmacist or doctor if a side effect is bothersome; constipation in particular is predictable and can usually be managed.

Serious effects are rare but include anaphylaxis (swollen throat or tongue, raised itchy rash, trouble breathing), changes in vision such as blurred or double vision, slowed or difficult breathing, and an unusual heartbeat. These need urgent medical help.

An extra dose can be dangerous, and the NHS says to seek help if you take more than prescribed; if sent to A&E, do not drive, and take the packet. If you miss a dose, take it as soon as you remember, unless more than 4 hours have passed since it was due, in which case ask for advice; skip it if the next is close and never double up.

Long use accustoms the body to morphine. Abrupt stopping can bring withdrawal symptoms, so the doctor reduces the dose gradually. Addiction is possible, and anyone worried about it should talk to their doctor.

The NHS says it may not suit people who have had an allergic reaction to morphine or another opioid, have a liver or heart condition, a lung condition such as asthma, a history of addiction to alcohol, prescription medicines or illegal drugs, a bowel condition such as an obstruction, or a head injury. Tell the doctor about any medical conditions.

Tell your doctor if you are pregnant or planning a pregnancy; morphine is sometimes used in pregnancy when needed, after a discussion of risks and benefits. It is not usually used while breastfeeding, though a doctor may recommend it if benefits outweigh risks or may choose another painkiller. If breastfeeding on it, speak to a professional or call 111 about any concerns for the baby.

Medicines that may not mix well include other opioids such as codeine and co-codamol, MAOI antidepressants, some medicines for nerve pain and seizures such as gabapentin, sedatives for insomnia or anxiety such as diazepam, some medicines for stomach ulcers and reflux, and some anti-sickness medicines. Cannabis, cocaine and heroin raise the risk of serious side effects.

It is best not to drink alcohol because it can cause sleepiness and increase serious side effects. Tell the prescriber about every medicine, herbal remedy and supplement you take.