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BMJ Group Medical Reference


This information is for people who have schizophrenia. It tells you about clozapine, a drug used to treat symptoms of schizophrenia. It is based on the best and most up-to-date research.

Does it work?

Yes. Clozapine reduces the symptoms of schizophrenia. It often works for people who have schizophrenia symptoms that can't be treated by other antipsychotics. But there is a risk of a serious side effect that damages your blood cells, so you need regular blood tests when you're taking clozapine.

What is it?

Clozapine (brand name Clozaril) is one of the newer antipsychotics. It comes as tablets.

If you take clozapine, there's a risk you'll get a dangerous side effect that damages your blood cells. So, you need to have blood tests every week or two when you're taking clozapine.

But you are less likely to get another problem, which affects the way your brain controls your muscles (called tardive dyskinesia) than if you were taking other antipsychotics.

The National Institute for Health and Clinical Excellence, which advises the government about which treatments should be used on the NHS, has written some guidelines about when doctors should use clozapine. [98] For more information, see Which type of antipsychotic drug should I take?

How can it help?

More people who take clozapine find that their symptoms get better than people who take standard antipsychotics. [99] [89] This means that people who take clozapine have fewer hallucinations, delusions, and disorganised thoughts, and are less likely to be agitated and suspicious.

In one large study, more than half the people who took clozapine found they got much better, compared with only a third of people who took standard antipsychotics. [99] Because clozapine works better, people are more likely to keep taking clozapine than other antipsychotics. This should mean they are less likely to have times when their symptoms come back (relapses). [99]

How does it work?

Your brain uses chemicals called neurotransmitters to carry messages between brain cells. Antipsychotics reduce the effects of a neurotransmitter called dopamine. Dopamine stimulates parts of your brain. Doctors think that if you have schizophrenia, it is because you have too much dopamine, and that causes the thoughts you have that couldn't be true (delusions) and the things you perceive that aren't really there (hallucinations).

Antipsychotics block the effect of dopamine. This has a calming effect, and makes hallucinations and delusions less intense. [100]

The newer antipsychotics such as clozapine block the effects of dopamine in a different way to the standard drugs. They can also affect the neurotransmitter serotonin. [100] This helps to explain why a drug such as clozapine may work better and have different side effects than one of the standard antipsychotics.

Last Updated: June 21, 2012
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.

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