Diamorphine is a type of painkiller. You have it for moderate to severe cancer pain. It can also reduce breathlessness caused by a build up of fluid in the lungs. 

You can only get diamorphine on prescription from your doctor. It is a type of opioid.

You pronounce diamorphine as dye-a-more-feen.

How does diamorphine work?

Diamorphine works by acting like the body’s natural painkillers known as endorphins. These control pain by blocking pain messages to the brain.

How do you have diamorphine?

You have diamorphine as an injection. This can be:

  • as an injection under your skin
  • into your bloodstream
  • as an injection into your muscle 

Injection under your skin (subcutaneous injection)

You usually have injections under the skin (subcutaneous injection) into the stomach, thigh or top of your arm.

You might have stinging or a dull ache for a short time after this type of injection but they don't usually hurt much. The skin in the area may go red and itchy for a while.

Some people have diamorphine through a small needle put under the skin and connected to a pump called a syringe driver. The pump gives you a small amount of diamorphine continuously. A nurse changes the pump every 24 to 48 hours.

Into your bloodstream

You might have treatment through a long plastic tube that goes into a large vein in your chest. The tube stays in place throughout the course of treatment. This can be a:

  • central line
  • PICC line
  • portacath

Injection into your muscle (intramuscular)

You have the injection into a muscle, usually into your buttock or upper thigh.

How often do you have diamorphine?

You usually have diamorphine every 4 hours, unless you have it as part of a syringe driver.

If you have too much diamorphine

Having too much diamorphine can cause severe breathing and heart changes. You should only take the dose of diamorphine prescribed by your doctor or nurse. Talk to your specialist team if you think you need a higher dose of painkillers. 

Go to your local accident and emergency (A&E) department if you have taken too much diamorphine and have slower breathing, low blood pressure and unconsciousness. Doctors may give you a drug called naloxone to stop the effects of diamorphine.

What are the side effects of diamorphine?

Side effects can vary from person to person. They also depend on what other treatment you are having. 

When to contact your team

Your doctor, nurse, or pharmacist will go through the possible side effects. They will monitor you closely during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects 

  • your side effects aren’t getting any better

  • your side effects are getting worse

Early treatment can help manage side effects better.

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects, but you might have some of them at the same time.

You might have one or more of these side effects. They include:


This drug may make you feel drowsy. Don’t drive or operate machinery if you have this.

If you become drowsy after having diamorphine for a while, it may mean that you need to lower your dose. Talk to your doctor or nurse before you change your dose. It is important to let them know. It can be very harmful to just stop taking diamorphine. You are likely to need to slowly reduce the amount you take.

Feeling or being sick 

Feeling or being sick is usually well controlled with anti sickness medicines. It might help to avoid fatty or fried foods, eat small meals and snacks and take regular sips of water. Relaxation techniques might also help.

It is important to take anti sickness medicines as prescribed even if you don’t feel sick. It is easier to prevent sickness rather than treat it once it has started.


You may feel less irritable and agitated once you start taking this drug. It can make you feel relaxed and drowsy.

Difficulty breathing

You may have difficulty breathing. If this happens, let your doctor or nurse know straight away. 

A severe allergic reaction 

A small number of people have an allergic reaction while having diamorphine as a drip into the bloodstream (intravenously). Tell your doctor or nurse immediately if you have shortness of breath, shock, low blood pressure, redness or swelling of the face, feeling hot, dizziness or a sudden need to pass urine.

You should not be given anymore diamorphine if this happens.


Constipation Open a glossary item is easier to sort out if you treat it early. Drink plenty of fluids and eat as much fresh fruit and vegetables as you can. Try to take gentle exercise, such as walking. Tell your healthcare team if you think you are constipated. They can prescribe a laxative.


Let your doctor or nurse know if you are sweating more than normal. Cutting out caffeine, nicotine and alcohol, and sipping cold or iced drinks may help to reduce sweating. 

Mental clouding

This is also known as brain fog. It can make you sleep more sleepy and less aware then normal. People feel as though their brains are foggy when this happens.


This drug might make you feel dizzy. Don’t drive or operate machinery if you have this.


You or the people around you may notice that you feel confused. Tell your doctor or nurse if this happens.

This may happen with large doses of diamorphine.

Narrowing of the pupils in your eyes

The pupils (black part) in your eyes may become narrower or look smaller. 

Changes in vision

You may get blurred or double vision. Do not drive or operate machinery if you have this symptom and speak to your doctor. 

Difficulty passing urine 

You might find it hard to pass urine. Let your doctor or nurse know if that happens.

Low blood pressure when you stand up or suddenly change position

Your blood pressure might drop when you stand up or change position suddenly. This is called postural hypotension. This may cause you to feel light headed or dizzy. 

Flushing of the skin 

The skin of your face may look red (flushed). 


You may feel as though the room is spinning. This is called vertigo. Let your doctor or nurse know if this happens.

Mood changes 

Mood changes can include feeling very sad or very happy. Tell your doctor or nurse if you’re having mood changes. They can arrange for you to talk to someone and give treatment if necessary.

Dry mouth 

A dry mouth is also called xerostomia. Talk to your nurse or doctor if you have a dry mouth. They can give you artificial saliva to help with this. It can also help to drink plenty of fluids during treatment with diamorphine.

Skin changes

Skin problems include a skin rash, dry skin and itching. This usually goes back to normal when your treatment finishes. Your healthcare team can tell you what products you can use on your skin to help.


Tell your doctor or nurse if you keep getting headaches. 

Loss of interest in sex

You may have less interest in sex, especially if you have diamorphine for a long period of time. 


Seeing or hearing things that are not there (hallucinations) can occur with this treatment. Speak to your doctor if this happens to you. 

Heart problems 

These include changes in your heart rhythm such as a slow heartbeat or palpitations. Tell your doctor or nurse straight away if you have any heart problems.

Tummy spasm

You might have pain in the right side of your abdomen, particularly after eating a meal. This may spread towards your right shoulder.

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drinks

Cancer drugs can interact with medicines, herbal products, and some food and drinks. We are unable to list all the possible interactions that may happen. An example is grapefruit or grapefruit juice which can increase the side effects of certain drugs.

Tell your healthcare team about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies. Also let them know about any other medical conditions or allergies you may have.

Pregnancy and contraception 

It is important not to become pregnant while having diamorphine. There is a risk that the baby could become dependent on it and suffer from withdrawal symptoms after birth.

Talk to your doctor or nurse about effective contraception.


It is not known whether this drug comes through into the breast milk. Doctors usually advise that you don’t breastfeed during this treatment.

Addiction to diamorphine

Some people worry about becoming addicted to diamorphine. When you take this kind of drug to control pain, it is unlikely that you will become addicted. But talk to your doctor or specialist nurse if you are worried. 

More information about this treatment

For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

  • Electronic Medicines Compendium 
    Last accessed July 2022

  • Morphine and alternative opioids in cancer pain: the EAPC recommendations
    G Hanks and others 
    British Journal of Cancer, 2001. Vol 84, Issue 5, Pages 587-593

  • What naloxone doses should be used in adults to reverse urgently the effects opioids or opiates?
    UK Medicines Information (UKMi) pharmacists for NHS healthcare professionals, July 2017 

Last reviewed: 
22 Dec 2022
Next review due: 
22 Dec 2025

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