Skip to main content

Haloperidol long-acting injection

Haldol Decanoate

Your doctor or nurse will inject haloperidol into a muscle in your buttocks. The effect of each injection will last for four weeks.

It is important you keep your regular appointments with your doctor or nurse.

There are a number of side-effects which you may experience from this treatment. If you are concerned about any of these, you should discuss them with your doctor.

Continue reading below

About haloperidol long-acting injection

Type of medicine

Antipsychotic injection

Used for

Easing the symptoms of schizophrenia and other similar mental health problems

Also called

Haloperidol decanoate; Haldol Decanoate®

Available as


Schizophrenia is a serious mental health condition that causes disordered ideas, beliefs and experiences. Haloperidol is used to relieve the symptoms of schizophrenia and other similar mental health problems. Such symptoms can include hearing, seeing, or sensing things that are not real, having mistaken beliefs, and feeling unusually suspicious.

Haloperidol works on the balance of chemical substances which act on the nervous system in your brain.

Long-acting, or 'depot', injections are used to maintain your recovery once your symptoms have been eased by taking tablets or capsules. The injection slowly releases haloperidol into your body and is given every four weeks. The main advantage of a depot injection is that you do not have to remember to take tablets every day.

Before having haloperidol long-acting injections

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start having haloperidol injections it is important that your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breastfeeding.

  • If you have a heart condition or blood vessel problems.

  • If you have liver, kidney, or prostate problems.

  • If you have a breathing problems.

  • If you have any of the following: epilepsy, Parkinson's disease, depression, increased pressure in your eyes (glaucoma) or a condition causing muscle weakness, called myasthenia gravis.

  • If you have ever had yellowing of your skin or the whites of your eyes (jaundice) or a blood disorder.

  • If you have a tumour on your adrenal gland (phaeochromocytoma).

  • If you have been told you have low levels of salts (electrolytes) in your blood.

  • If you have ever had an allergic reaction to any medicine.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

Continue reading below

How to use haloperidol long-acting injection

  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about haloperidol and a full list of side-effects which you may experience from having it.

  • Haloperidol long-acting injection will be given to you by your doctor or nurse. It is given by injection into a muscle in your buttocks.

  • If you haven't received an injection like haloperidol before, a small dose is usually given as a test before you have a normal dose. This is to see how well you tolerate the injection.

  • You may be asked to continue taking your current tablets or capsules for a short while after you have had your first injection. This is because it can take a few weeks before you feel the full effect from the injection.

  • If you miss an appointment for an injection, you should contact your doctor's surgery to make another appointment as soon as possible. This is because the injection should be given to you without further delay.

  • Treatment with haloperidol injection may need to continue for several months or even years. Your dose will be reduced gradually to make sure your symptoms don't return.

Getting the most from your treatment

  • Your treatment will require careful monitoring to make sure that you get the best possible benefit from haloperidol. Keep your regular doctor's appointments so your progress can be checked. You will need to have some tests from time to time.

  • If you are having any dental treatment or an operation, tell the person carrying out the treatment which medicines you are taking. This is important because haloperidol may interfere with any anaesthetic you receive.

  • If you buy or take any 'over-the-counter' medicines, check with a pharmacist that they are suitable for you to take with haloperidol.

  • If you drink alcohol, ask your doctor for advice about drinking while you are on haloperidol. Alcohol may increase the chance that you experience side-effects and may not be recommended for you.

  • Smoking may affect the amount of haloperidol in your body. Let your doctor know if you start or stop smoking while you are having haloperidol.

  • Haloperidol may cause your skin to become more sensitive to sunlight than normal. Use a sunscreen that protects against UVA light and has a sun protection factor (SPF) of at least 15, especially in strong sunlight or until you know how your skin reacts. Do not use sunbeds.

  • If you have diabetes you may need to check your blood glucose more frequently, as haloperidol may affect the levels of sugar in your blood. Your doctor will be able to advise you about this.

Continue reading below

Can haloperidol long-acting injection cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Common haloperidol side-effects

What can I do if I experience this?

Pain and redness at the site of the injection

This should quickly pass. If the area becomes swollen or 'lumpy', let your doctor or nurse know

Feeling dizzy or sleepy, blurred vision

If this happens, do not drive and do not use tools or machines. Do not drink alcohol

Dry mouth

Try chewing sugar-free gum or sucking sugar-free sweets

Stomach upset

Stick to simple meals - avoid rich or spicy food


Drink plenty of water and eat a well-balanced diet


Ask your pharmacist to recommend a suitable painkiller. If the headaches continue, speak with your doctor

Feeling shaky or restless, unusual or uncontrollable muscle movements, increased saliva

Speak with your doctor as soon as possible about any of these. Your treatment may need adjusting

Changes in your weight, difficulty sleeping, mood changes, stuffy nose, changes in sexual ability, breast enlargement, production of breast milk, menstrual problems, fast heartbeat, difficulty passing urine, skin rash

Discuss these with your doctor if any become troublesome

Important: if you experience any 'flu-like' symptoms including any muscle stiffness, a very high temperature, feeling confused or sweaty, and a fast heartbeat, you must contact your doctor immediately. These may be signs of a rare but serious condition known as neuroleptic malignant syndrome.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

How to store haloperidol long-acting injection

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

symptom checker

Feeling unwell?

Assess your symptoms online for free