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What is olanzapine?

Olanzapline is pronounced ‘o-lanz-a-pean’.

Olanzapine (also called Zyprexa®) is mainly used to help treat the symptoms psychosis, schizophrenia and mania, and to prevent these symptoms coming back.

It is sometimes used to help the symptoms of anxiety, depression and eating problems.

It is made as tablets, a melt-in-the-mouth tablet, short-acting injection and a long-acting injection.


Olanzapine is often used in adults but it is not “licensed” or officially approved for people under the age of 18. This is because it has not been fully studied in this younger age group. If you are under 18 you may be offered this medicine because we have experience of it and we know it helps adults.

What does olanzapine help?

Olanzapine can help with psychosis (or ‘losing touch with reality’) including:

  • hallucinations (seeing or hearing things that are not there)
  • delusions (thinking something is true when is it not)

Olanzapine can also help with mania (feeling very high) and depression (feeling very low).

How and when should I take olanzapine?

Swallow the tablets with some water whilst sitting or standing. This is to make sure that they reach the stomach and do not stick in your throat.

For the melt-in-your-mouth tablets, just put them onto your tongue and they will dissolve quickly.

You do not have to take it with food.

If the label says to take it once a day, it is best to take it at bedtime as it may make you drowsy when you first start taking it.

How long will I have to wait before it works?

This will depend on what you are taking it for.

The effect usually starts in 1 or 2 weeks, and builds over the next couple of weeks.

How long will I need to take olanzapine for?

This will depend on what you are taking it for.

It may be for several months or years.

What if I do not want to take olanzapine anymore?

Do not stop taking olanzapine suddenly.

It is better not to do this without talking it over first with other people such as your family, prescriber, nurse, pharmacist or other healthcare professional.

It normally works out much better if you stop medication in a planned way at a time when your stress levels are lower, rather around exam times, mid-winter and life events.

Your symptoms can return if treatment is stopped too early. This may happen some weeks or even months after you stop taking olanzapine.

When the time comes, you should stop olanzapine by gradually reducing the dose over several weeks.

What should I do if I forget to take a dose?

Start again as soon as you remember if within about 12 hours of your next dose. After this just take the next dose as normal.

Do not try to catch up by taking 2 doses at once as you may get more side-effects.

Can I cycle or drive while I am taking olanzapine?

You may feel a bit light-headed at first when taking olanzapine.

Until this wears off, or you know how olanzapine affects you, be careful cycling and, do not drive or operate machinery.

What are the side effects of olanzapine?

Very common

More than 1 in 10 people might get these:

  • Fatigue and sleepiness. This may happen early on and usually wears off. If you feel like this for more than a week after starting, tell your prescriber. It may be possible to adjust your dose slightly.
  • Weight gain.  You might feel like eating more whilst taking this medication.  A diet full of  cereal, vegetables and fibre may help to prevent you gaining weight.


Fewer than 1 in 10 people may get these:

  • Postural hypotension. This is a drop in blood pressure when your stand up. To avoid this, stand up slowly. Discuss this with your prescriber next time you meet.
  • Dry mouth or not much spit. Suck on sugar-free gum or boiled sweets. If it is bad, your prescriber may be able to give you a mouth spray.
  • Constipation and not being able to poo. Make sure you eat enough fibre, cereals or fruit, drink enough fluid, and keep active. If this does not help, ask your prescriber or pharmacist for a mild laxative.
  • Swollen ankles. Discuss this with your prescriber next time you meet.
  • Diabetes and high blood sugar level. You might lose weight, pass more urine, and feel thirsty and hungry all the time. Tell your doctor if you get these symptoms, and then you can have some simple tests.

Rare side effects

Please see your prescriber if you get any of these rare side effects:

  • D.R.E.S.S. rash.  This is a sudden rash seen anywhere on the skin, fever, and swollen glands. If this happens, stop taking olanzapine and contact your prescriber in the next day.
  • Neuroleptic malignant syndrome (NMS).  Symptoms include: fever, sweating, confusion, racing heart, muscle stiffness and difficulty moving.  See your prescriber straight away if you have had a change in dose or taken other antipsychotics.

Some side effects are the brain getting used to a medicine and these usually wear off in a few days or weeks. Starting slower may help. If you think you might have a side effect, you should ask your prescriber, pharmacist or other healthcare professional.

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Please note: this is a generic information sheet relating to care at Sheffield Children’s NHS FT. These details may not reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If this information has been translated into another language from English, efforts have been made to maintain accuracy, but there may still be some translation errors. If you are unsure about any of the guidance in this resource or have specific questions about how it relates to your child, always ask your healthcare professional for further advice.

Resource number: MH77

Resource Type: Article

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