Explains what antipsychotics are used for, how the medication works, possible side effects and information about withdrawal.

What are antipsychotic drugs used for?

You are most likely to be given antipsychotic drugs if you are experiencing psychosis, either as a one-off episode or as part of an ongoing illness. You may also be given an antipsychotic for other mental health problems.


If you are having a psychotic episode, you may perceive things and interpret events differently from those around you. You may hear voices, see things other people can’t see (hallucinations) or have ideas that are not shared by those around you (delusions). You might believe, for example, that you are under the control of an outside force.

Psychotic illnesses include schizophrenia and mania, but you may also experience brief episodes during severe depression or a physical illness, or sometimes because of taking street drugs, such as amphetamines, cocaine or cannabis.

(For more information, see Psychotic experiencesHow to cope with the early signs of mental health problemsThe mental health effects of street drugsBipolar disorder and Schizophrenia.)

Antipsychotics are not a cure for psychosis, but are often effective in controlling its symptoms, and may help you to return to normal life. You may find that rather than stopping your psychotic experiences, e.g. hearing voices, the drugs just stop you feeling so bothered by them.

They may:

  • control anxiety and serious agitation, so that you feel less threatened
  • reduce incoherent speech and muddled thinking
  • reduce confusion
  • lessen delusions and hallucinations
  • reduce violent, disruptive behaviour
  • reduce mania.

Other conditions

Antipsychotics are also sometimes prescribed for anxiety, in very low doses, and to supplement antidepressants if you are severely depressed. They are also sometimes used to control agitation and psychotic experiences in dementia.

Occasionally they are used for treating physical problems, such as persistent hiccups, problems with balance, and nausea.

The antipsychotic that worked gave me a break from symptoms that were very difficult to live with. Once my depression had lifted I was able to stop taking it.

What types of antipsychotic are there?

The first generation (older) antipsychotics, developed in the 1950s, divide into various chemical groups which act in a very similar way and have very similar side effects, but vary slightly in how likely you are to get the different types of side effects: for example, some cause more movement disorders and some are less sedating than others. See 'The different types of antipsychotics' for more details on the individual drugs and their side effects.

The second generation (newer) antipsychotics. Most of the newer antipsychotics were first licensed in the 1990s, developed with the aim of reducing the severe movement disturbances associated with the older drugs. Some of them also have fewer of the side effects associated with raised prolactin levels (see ‘Sexual side-effects’). However they do cause serious metabolic side effects including gross weight gain. See 'The different types of antipsychotics' for more details on the individual drugs and their side effects. 

Which type of antipsychotic should I be taking?

Not everybody finds antipsychotics helpful and they can have a large number of side effects which affect a lot of people who take them, to some extent. If you find the medication helps with your symptoms, you may feel it worth putting up with a few side effects, but if the drugs don’t seem to be helping much, the side effects may be difficult to tolerate. You may need to try one or two different drugs before you find the one that suits you best.


Antipsychotic drugs treat the ‘positive’ symptoms of schizophrenia, which include delusions and hearing voices. The ‘negative’ symptoms include feeling apathetic, not looking after yourself, and being unable to concentrate.

Older antipsychotics usually have no effect on the negative symptoms, and some of the side effects may make them worse.

Newer antipsychotics often help with both types of symptoms. You should be given a choice about which type of antipsychotic to take, but if you are unable to make a choice, then you should be given a newer drug. NICE (The National Institute for Health and Clinical Excellence) recommends that newer antipsychotics should be used:

  • as a first-line treatment, if you are newly diagnosed with schizophrenia. The starting dose should be at the lower end of the standard range
  • if you have an acute episode of schizophrenia, and you are not able to discuss the choice of drug with the doctor
  • if you have had unacceptable side effects on older antipsychotics
  • if you have had a relapse, and your symptoms did not respond well to the older drugs. 

If you are already on an older antipsychotic, and your symptoms are responding well, without causing you unacceptable side effects, there’s no need to change to a newer drug. If neither an older nor a newer antipsychotic has controlled your symptoms after you have taken them for six to eight weeks, your doctor should suggest you try clozapine.

Other conditions

If you are taking an antipsychotic for bipolar disorder or depression, you are most likely to be prescribed one of the newer drugs. For anxiety, either type might be used, at very low doses.

Who shouldn’t take antipsychotics?

It is important that your doctor knows about any medical conditions you have and any treatment you are already receiving when they are prescribing an antipsychotic and deciding which one may be most suitable for you.

If you have any of the following, you should use these drugs with caution:

  • liver or kidney disease
  • cardiovascular (heart and circulation) disease – or a family history of this (see 'Effects on the heart')
  • family history of diabetes
  • Parkinson’s disease
  • epilepsy
  • depression
  • myasthenia gravis (a rare disease affecting nerves and muscles)
  • an enlarged prostate
  • a history of glaucoma, an eye disease (see 'Eye problems')
  • lung disease with breathing problems
  • some blood disorders. 

Antipsychotics should not be given to people with phaeochromocytoma (a type of tumour causing very high blood pressure) or anyone who is semi-conscious, unconscious or in a coma.

Older people

Doctors should also prescribe them with caution to older people. This is because they may be prone to drops in blood pressure when standing up, leading to falls, and also to both high and low body temperature.

Expectant and new mothers

As a general rule, you should avoid taking any drugs during pregnancy and while breastfeeding, unless the benefits to you are likely to outweigh the risk to the baby. If possible, avoid all drugs at least during the first three months. Prochlorperazine (Stemetil), in particular, is associated with malformations in the developing baby during this period.

There have also been reports of temporary muscle disorders in newborn babies, if antipsychotics are used in the last three months of pregnancy. Because long-acting drugs take time to clear from the body, it’s important to take your final dose six to eight weeks before the baby’s expected delivery date. It’s very important to discuss any concerns with your doctor, midwife and other professionals responsible for your health during pregnancy and delivery.

The manufacturers advise women against taking the newer antipsychotics if you are breastfeeding. It’s best to avoid antipsychotics altogether, if possible. Ask your doctor and your pharmacist about the safety of any drug you are advised to take. 

How do the drugs work?

Most antipsychotics block the effects of dopamine, one of the brain chemicals that carry messages between cells in different areas of the brain. Blocking dopamine reduces the flow of messages, which may be too frequent in psychotic states. Many of the drugs make you feel very slowed down and sleepy, and some people have suggested that they work by causing Parkinsonism – not just the physical symptoms, which are well recognised as side effects, but also the psychological symptoms of this disease such as not feeling your emotions and losing interest in doing your usual activities.

Most antipsychotics affect other brain chemicals too, such as serotonin and noradrenaline, and this causes additional side effects.

How quickly do they act?

This depends partly on how you take them:

  • By mouth. If you take them by mouth, in tablet or in syrup form, the sedative effect usually takes a few hours; the liquid form may act more quickly than the tablets.
  • Emergency injection. In an emergency you may be given an injection into a muscle, and then the sedative effect is rapid and reaches a peak within an hour.
  • Depot injection. Some drugs are available in a slow-release form given by deep injection, known as a ‘depot’, into a muscle. Depot injections do not have a fast action, and are given every two to six weeks. You would not normally be given a depot unless you had taken the drug in tablet form already and it was helpful. 

However you take the drugs, they may calm you down quite quickly, but the psychotic symptoms, such as voices, may take days or weeks to suppress.

What dosage should I be on?

You have a right to know what dosage you have been prescribed, and these vary widely. For example, chlorpromazine (Largactil) can be prescribed in tablet form to physically healthy adults in doses ranging from 75mg up to 1,000mg daily.

Because antipsychotics can have very serious side effects, the NICE guidelines on the treatment of schizophrenia suggest that doctors prescribe antipsychotics at the lowest effective dose to reduce your symptoms, and increase gradually if necessary. The aim should be to find the dose that lets you lead as normal a life as possible. You should not be given a high starting dose.

High doses of the older drugs can make you feel like a zombie, with little expression on your face and strange movements, and a loss of interest in life. They can make it very difficult for you to move normally, to get up and get going in the morning, and to take part in normal activities.

Moderate to high doses increase the risk of tardive dyskinesia, which is a serious problem causing spontaneous movements.

For many people, low maintenance doses are as effective as higher doses. As you get older, your body gets less efficient at dealing with drugs generally, so older people need smaller doses of drugs, and their health is at risk if they are given too high a dose.

If the medication is not working, it’s important for doctors to think about trying a different drug rather than automatically putting up the dose of the one you started with. 

Maximum dosage

The British National Formulary (BNF – the main drug reference book for prescribers) gives maximum doses for some, but not all, of the antipsychotics (see details for individual drugs). Generally, the drugs aren’t licensed for use above these dosages, but doctors can give you a higher dose, at their discretion. If you are in hospital, they may also prescribe medication to be given ‘as necessary’ (usually referred to as p.r.n.) which can mean in addition to your regular dose. As a result, your total dose could be above the BNF maximum. In this case, your psychiatrist has a duty to review your total dosage daily.

If you are taking more than one antipsychotic drug, you can work out the dose of each (including p.r.n. prescribing, as long as you know each dose) as a percentage of the maximum recommended in the BNF. Add the percentages together to see if you are taking more than 100 per cent in total. You can also ask your doctor or a pharmacist to help you work this out. If you think you are taking too much medication, you can ask your doctor to review it.

Why do people take more than one antipsychotic?

Your doctor may want to prescribe more than one antipsychotic at a time. This is known as polypharmacy. This could mean that a doctor prescribes an oral drug as well as a depot injection, or an older drug as well as a newer one.

This may happen:

  • if the drug you are currently taking doesn’t seem to be working well enough
  • when a careful combination of two drugs controls your symptoms best; the decision has to be made for each person on an individual basis
  • you are detained in hospital under the Mental Health Act 1983. (You are far more likely to be taking more than one antipsychotic, or to be on a high dose, than someone who is a voluntary patient.)

However, in most cases, doctors should avoid combining the different types of antipsychotics. 

  • The newer drugs cause fewer movement disorders (see 'Neuromuscular side effects') and antimuscarinic effects than the older ones, and this benefit is lost if you are taking both at the same time.
  • The BNF does not recommend polypharmacy, because even though the individual drugs may be within the recommended dose range (see opposite), patients may end up having a high total dose. 
  • The NICE guidelines say that it’s best to use a single drug, and that two or more antipsychotics should not be given at the same time, except for short periods when you are switching from one to another.
  • Research has shown that adding a second drug doesn’t usually improve the outcome very much, but does increase the side effects, which can diminish your quality of life, and may even be life-threatening.

What is rapid tranquillisation?

In an emergency situation, if you are behaving in a way that might be putting yourself or other people at risk, doctors may decide you need something to calm you down as quickly as possible. This means you may be given drugs by injection. 

The drugs most likely to be used are the older antipsychotics Clopixol Acuphase or haloperidol, or the newer drug olanzapine. The antipsychotic may be combined with a benzodiazepine tranquilliser (see Sleeping pills and minor tranquillisers).

The NICE guidelines recommend lorazepam (a benzodiazepine), with haloperidol or olanzapine. If you are given haloperidol at a high dose, you may need an anti-Parkinson’s drug to minimise the side effects.

The NICE guidelines also say that rapid tranquillisation may be traumatic, and afterwards you should be given the opportunity to discuss it with hospital staff, and to write your own record of the experience if you wish, to be kept in your hospital notes.

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