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Antipsychotic medicines

In this series:SchizophreniaPsychosis

Antipsychotics are medicines that are mainly used to treat schizophrenia or mania caused by bipolar disorder. There are two main types of antipsychotics: atypical antipsychotics and older antipsychotics. Both types are thought to work as well as each other. Side-effects are common with antipsychotics. Regular tests may be needed to monitor for side-effects on some of these medicines.

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What are antipsychotics?

Antipsychotics are a group of medicines that are mainly used to treat mental health illnesses such as schizophrenia, or mania (where you feel high or elated) caused by bipolar disorder. They can also be used to treat severe depression and severe anxiety. Antipsychotics are sometimes also called major tranquillisers.

Types of antipsychotics

There are two main types of antipsychotics:

Antipsychotics are available as tablets, capsules, liquids and depot injections (long-acting). They come in various different brand names.

Older antipsychotics have been used since the 1950s and are still prescribed today. Newer antipsychotics were developed in the 1970s onwards. It was originally thought that these medicines would have fewer side-effects than the older type of antipsychotics. However, we now know that they can also cause quite a few side-effects.

How do antipsychotics work?

Antipsychotic drugs are thought to work by altering the effect of certain chemicals in the brain, called dopamine, serotonin, noradrenaline and acetylcholine. These chemicals have the effect of changing behaviour, mood and emotions. Dopamine is the main chemical that these medicines have an effect on.

By altering the effects of these chemicals in the brain they can suppress or prevent you experiences such as:

  • Hallucinations (such as hearing voices).

  • Delusions (having ideas not based on reality).

  • Thought disorder.

  • Extreme mood swings that are associated with bipolar disorder.

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When are antipsychotics usually prescribed?

As discussed above, antipsychotics are usually prescribed to help ease the symptoms of schizophrenia, mania (caused by bipolar disorder), severe depression or severe anxiety. Normally they are started by a specialist in psychiatry.

For many years antipsychotic drugs were used to calm elderly people who had dementia. However, this use is no longer recommended. This is because these medicines are thought to increase the risk of stroke and early death - by a small amount.

Risperidone is the only antipsychotic recommended for use in these people. Even then, it should only be used for a short period of time (less than six weeks) and for severe symptoms.

Which antipsychotic is usually prescribed?

The choice of antipsychotic prescribed depends upon what is being treated, how severe the symptoms are and if there are any other health problems. There are a number of differences between the various antipsychotic medicines.

Some are more sedating than others and, therefore, one may be better for one individual than for another. A specialist in psychiatry usually recommends which to use in each case. It is difficult to tell which antipsychotic will work well for any particular individual. If one does not work so well, a different one is often tried and may work well.

It is thought that the older and newer types of antipsychotics work as well as each other. The exception to this is clozapine - it is the only antipsychotic that is thought to work better than the others. Unfortunately, clozapine has a number of possible serious side-effects, especially on the blood cells. This means that people who take clozapine have to have regular blood tests.

In some cases, an injection of a long-acting antipsychotic medicine (depot injection) is used once symptoms have eased. The medicine from a depot injection is slowly released into the body and is given every 2-4 weeks. This aims to prevent recurrences of symptoms (relapses). The main advantage of depot injections is that you do not have to remember to take tablets every day.

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How well do antipsychotics work?

It is thought that, for every 10 people who take these medicines, 8 will experience an improvement in their symptoms. Unfortunately, antipsychotics do not always make the symptoms go away completely or for ever.

A lot of people need to take them in the long term even when they have returned to feeling well. This is in order to stop their symptoms from coming back. Even when taking these medicines on a long-term basis and when they are helping, sometimes symptoms can come back.

How long do antipsychotics take to work?

Symptoms may take 2-4 weeks to ease after starting medication and it can take several weeks for full improvement. The dose of the medicine is usually built up gradually to help to prevent side-effects.

What is the usual length of treatment?

This depends on various things. Some people may only need to take them for a few weeks but others may need to take them long-term (for example, for schizophrenia). Even when symptoms ease, antipsychotic medication is normally continued long-term in illnesses like schizophrenia.

This aims to prevent relapses, or to limit the number and severity of relapses. However, where there is only one episode of symptoms of schizophrenia that clears completely with treatment, some psychiatrists will suggest trying to stop medication after 1-2 years.

Stopping antipsychotics

Decisions about stopping an antipsychotic should always be made after discussion with a psychiatrist. This is to help to decide whether stopping is a sensible plan and, if so, how that should be done.

These medicines are usually stopped slowly over a number of weeks. Stopping an antipsychotic medicine suddenly can cause someone to become unwell quite quickly. By reducing the dose slowly it is easier to see what effect the lower dose has on symptoms.

Side-effects of antipsychotics

Side-effects can sometimes be troublesome. There is often a trade-off between easing symptoms and having to put up with some side-effects from treatment. Different antipsychotic medicines can have different types of side-effects.

Sometimes one medicine causes side-effects in some people and not in others. Therefore, it is not unusual to try two or more different medicines before one is found that is best suited to an individual.

Common side-effects of antipsychotics

The following are the main side-effects that sometimes occur. However, it is helpful to read the information leaflet that comes in each medicine packet for a full list of possible side-effects.

Common side-effects include:

  • Dry mouth, blurred vision, flushing and constipation. These may reduce over time on the medication.

  • Drowsiness (sedation) is also common but may be an indication that the dose is too high. A reduced dose may be an option.

  • Weight gain occurs for some patients. Weight gain may increase the risk of developing diabetes and heart problems in the longer term. This appears to be a particular problem with some of the atypical antipsychotics - notably, clozapine and olanzapine.

  • Movement disorders develop in some cases. These include:

    • Parkinsonism - this can cause symptoms similar to those that occur in people with Parkinson's disease - for example, tremor and muscle stiffness.

    • Akathisia - this is like a restlessness of the legs.

    • Dystonia - this means abnormal movements of the face and body.

    • Tardive dyskinesia (TD) - this is a movement disorder that can occur in some people who have taken antipsychotics for several years. It causes rhythmical, involuntary movements which are usually lip-smacking and tongue-rotating movements, although it can affect the arms and legs too. About 1 in 5 people treated with typical (older) antipsychotics eventually develop TD.

Atypical antipsychotic medicines are thought to be less likely to cause movement disorder side-effects than typical antipsychotic medicines. This reduced incidence of movement disorder is the main reason why an atypical antipsychotic is often used first-line.

Atypicals do, however, have their own risks - in particular, the risk of weight gain. If movement disorder side-effects occur then other medicines can be used to try to counteract them.

Will I need any tests while taking an antipsychotic?

Regular monitoring for side-effects is advised when taking an antipsychotic. Which tests are needed and how often depends on which antipsychotic being taken.

Usually a psychiatrist will recommend a blood test before starting treatment. The tests look at:

  • The number of blood cells.

  • How well the kidneys and liver are working.

  • How much lipid (fat) is in the blood.

  • Sugar levels to look for diabetes.

The blood level of prolactin (a hormone) may also be measured before starting treatment and six months later. Usually it is then measured every year after this.

The prolactin level is measured because sometimes antipsychotics can make you produce too much of this hormone. Too much prolactin it can lead to breast milk being produced and to reduction in fertility.

Clozapine side-effects

When taking clozapine, the white blood cell (leukocyte) and differential blood counts must be normal before treatment is started. After beginning treatment, a full blood count should be taken every week for 18 weeks, then at least every two weeks after that.

If clozapine is continued, and the blood count is stable after one year, then monitoring can reduce but should occur at least every four weeks, and for four weeks after finishing. These tests may be repeated in the first three or four months of treatment. After this they are normally done every year unless there are particular reasons to do them more frequently.

Weight and blood pressure are usually measured before starting treatment and every few weeks after this for the first few months. After this they are normally measured every year.

Clozapine can only be prescribed by psychiatrists in the UK (who have to be registered with a clozapine monitoring system) and can only be obtained from specific pharmacies, usually in hospitals.

Prolactin side-effects

Who cannot take antipsychotics?

Typical (older) antipsychotics are contraindicated in people who are using medication which can cause depression in the central nervous system (eg, benzodiazepines or opioid medication), in people with severe heart abnormalities, in people with a history of a seizure disorder and in people with a high risk of acute glaucoma. They might be used with caution in men with benign enlargement of their prostate gland.

Atypical antipsychotics are not recommended in elderly people with dementia as they may increase the risk of stroke. They are also not recommended with certain other medications that can slightly affect heart rhythm.

As with all medications, the advice in pregnancy is to only take medications if the benefits outweigh the risks. In someone on antipsychotics it will often be recommended that they stay on the medication during pregnancy as stopping them could cause symptoms to recur. Newer antipsychotics have not been shown to cause any harm to the baby during pregnancy although babies are often monitored for potential withdrawal symptoms after the birth.

Can I buy antipsychotics?

No - they are only available on prescription.

Further reading and references

Article history

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

  • Next review due: 12 May 2028
  • 14 Jun 2023 | Latest version

    Last updated by

    Dr Pippa Vincent, MRCGP

    Peer reviewed by

    Dr Colin Tidy, MRCGP
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