Diamorphine is a 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.

How it works

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

How you have diamorphine

You can have diamorphine in a number of different ways. You might have it as:

  • an injection under your skin (subcutaneous)
  • an injection into your vein (intravenous)
  • as tablets that you swallow whole

The dose you have depends on the amount of pain you have. You usually start by having a low dose. And your doctor or nurse will gradually adjust the dose depending on your needs. 

As an injection under the skin

You usually have diamorphine as an injection into the fatty tissue just under the skin. This might be in your thigh, stomach or upper arm. You might have stinging or a dull ache for a short time after this 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.

As an injection into your vein

You might have diamorphine into your bloodstream. You usually have it through a thin, short tube (a cannula) put into a vein in your arm or the back of your hand. Or you may have it through a central line, a portacath or a PICC line. These are long, plastic tubes that give the drug directly into a large vein in your chest.  

Taking your tablets

You must take tablets according to the instructions your doctor or pharmacist gives you. You should take the right dose, no more or less.

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.

When you have diamorphine

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


You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

Side effects

How often and how severe the side effects are can vary from person to person. They also depend on what other treatment you are having. For example, your side effects could be worse if you are also having other drugs or radiotherapy.

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:

Drowsiness and dizziness

This drug may make you feel drowsy or dizzy. 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. Avoiding fatty or fried foods, eating small meals and snacks, drinking plenty of water, and relaxation techniques can all 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 treating it once it has started.


Constipation 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 doctor or nurse if you are constipated for more than 3 days. 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. 


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

Narrowing of the pupils in your eyes

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

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 nurse will tell you what products you can use on your skin to help.


People taking diamorphine for weeks or months can develop a physical and psychological dependence on the drug. This causes withdrawal symptoms if the drug is stopped. 

Psychological dependence is more likely to happen in people who have, or have had problems with alcohol or drug use. Talk to your doctor or specialist nurse if you are worried about becoming addicted to diamorphine.


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.

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, redness or swelling of the face, feeling hot, dizziness or a sudden need to pass urine.

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

Diamorphine can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

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 go to the electronic Medicines Compendium (eMC) website.

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

Last reviewed: 
08 Apr 2019
  • Electronic Medicines Compendium 
    Last accessed April 2019

  • 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 

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