Find out about the side effects of the painkiller drug morphine.
Tell your doctor or nurse if you have any side effects so they can help you manage them. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.
Common side effects
Each of these effects happens in more than 10 in every 100 people (more than 10%). You might have one or more of them.
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.
You might feel sick or be sick. Anti sickness injections and tablets can control it. Tell your doctor or nurse if you feel sick. You might need to try different anti sickness medicines to find one that works.
- Avoid eating or preparing food when you feel sick.
- Avoid hot fried foods, fatty foods or foods with a strong smell.
- Eat several small meals and snacks each day.
- Relaxation techniques help control sickness for some people.
- Ginger can help – try it as crystallised stem ginger, ginger tea or ginger ale.
- Try fizzy drinks.
- Sip high calorie drinks if you can’t eat.
This happens in about 3 out of every 10 people (30%).
Drowsiness may be a problem at first or when your dose is increased, but usually wears off after a few days.
Do not operate machinery or drive if you are feeling drowsy.
Occasional side effects
Each of these effects happens in 1 to 10 in every 100 people (1 to 10%). You might have one or more of them.
Let your doctor or nurse know if you have headaches. They can give you painkillers.
Don’t drive or operate heavy machinery if you feel dizzy.
Your mouth might get very dry, which can be uncomfortable. Various things can help.
- Try to drink at least 3 pints (one and a half litres) of fluid a day.
- Choose meals that are moist.
- Use gravies and sauces to make swallowing easier.
- Take regular sips of water with your meal to help you chew and swallow your food.
- Suck small amounts of ice chips to refresh your mouth.
- Chew sugar free chewing gum.
- Try eating fresh pineapple.
- Get your doctor or nurse to give you medicines to stimulate your salivary glands.
- Ask your doctor about artificial saliva products, such as tablets, mouthwashes, gum, pastilles, and toothpaste.
- It is very important to have regular check ups with your dentist.
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.
You may have sudden jerking of the body due to muscle contractions. Talk to your nurse or doctor if you have this.
You or the people around you may notice that you feel confused. Tell your doctor or nurse if this happens.
The pupils (black part) in your eyes may become narrower or look smaller.
You may have less interest in sex with this treatment.
Talk to your doctor or nurse if you’re having problems sleeping. It can help to change a few things about when and where you sleep.
- Go to bed and get up at the same time each day.
- Make sure the temperature is right.
- Spend time relaxing before you go to bed - have a bath, read or listen to music.
- Do some light exercise each day to help tire yourself out.
- Avoid caffeine (coffee, tea, chocolate and cola drinks) after early afternoon.
- Have a light snack before you go to bed to stop hunger waking you up.
You may have a griping pain in your stomach.
You might feel very tired or find you are falling asleep during the day. Do not drive or operate machinery. Let your doctor know straight away.
You might lose your appetite a bit during this treatment. If this happens you can try eating several small meals and snacks throughout the day.
Your doctor or nurse can recommend high calorie drinks to sip if you are worried about losing weight.
Don't fill your stomach with a large amount of liquid before eating.
Try to eat high calorie foods to keep your weight up.
Let your doctor or nurse know if you are sweating much more than normal.
- Cut out coffee, tea and nicotine.
- Cut down on alcohol.
- Sip cold or iced drinks.
- Wear layers of light clothing so you can take clothes off if you overheat.
- Have layers of bedclothes to remove as you need to.
- Wear natural fibres such as silk or cotton instead of man made fabrics.
A rash can also be itchy. Tell your doctor or nurse if you have a skin rash. They can prescribe medicine to stop the itching and soothe your skin.
Rare side effects
Each of these effects happens in fewer than 1 in 100 people (1%). You might have one or more of them.
A small number of people have an allergic reaction while having this treatment.
Tell your doctor or nurse immediately if you have any of these symptoms:
- a rash
- shortness of breath
- redness or swelling of the face
- feeling hot
- a sudden need to pass urine
This drug can cause you to have mood changes such as anxiety and agitation.
Speak to your doctor or nurse if you feel different. They can give you advice to help you.
It can help to warn your family that you might get this. You or your family members should let your doctor or nurse know if you have it.
Seeing or hearing things that are not there (hallucinations) can occur with this treatment. Speak to your doctor if this happens to you.
Tell your doctor or nurse straight away if this happens.
Let your doctor or nurse know if you have stiffness anywhere during or after having treatment. There are lots of ways to treat it, including relaxation and painkillers.
You might find it hard to pass urine. Let your doctor or nurse know if that happens.
These include your blood pressure going down or changes in your heart rhythm such as a slow heartbeat or palpitations.
You may have a slower breathing. If this happens, let your doctor or nurse know straight away. You may need a lower dose of morphine.
This is caused by changes in the nerve endings. It might feel like pins and needles.
This can make it difficult to do fiddly things such as doing up buttons. Speak to your doctor or nurse if you have this.
This drug can cause nerve damage which can lead to sudden fainting or unconsciousness and loss of ability to speak.
Tell your doctor or nurse if you have any changes to your eyesight.
A feeling of falling or the room spinning is also called vertigo. Talk to your doctor or nurse if you have this.
Your skin may appear flushed.
A build up of fluid in the lungs can cause breathlessness. Speak to your doctor or nurse if you have this.
Tell your nurse or doctor if you have heartburn or acid reflux. They can give you anti acid medicine.
Sleeping upright in bed helps to prevent heartburn. You can use pillows or cushions to support yourself.
Changes in taste can make you go off certain foods. Many people go off tea and coffee, for example. You might also find that some foods taste different. Some people find that they prefer to eat spicier foods.
Your taste usually gradually goes back to normal when your treatment is over. It may take a few weeks.
- Choose foods that have strong flavours, such as herbs, spices, marinades and sauces if all your food tastes the same.
- Season your food with spices or herbs, such as rosemary, basil and mint.
- Garnish cold meat or cheese with pickle or chutney.
- Try lemon or green tea if tea or coffee taste strange.
- Sharp tasting fizzy drinks such as lemonade or ginger beer are refreshing.
- Some people find that cold foods taste better than hot foods.
Talk to your doctor or nurse about this.
More information about this treatment
We haven't listed all the very rare side effects of this treatment. For further information see the electronic Medicines Compendium (eMC) website.
You can report any side effect you have that isn’t listed here to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.