Olanzapine ("oh-LAN-za-peen") is an atypical antipsychotic medicine which can be used to treat mania, schizophrenia and bipolar disorder

This page will give you general information about olanzapine. It is not medical advice. Always talk to your doctor about your situation and whether this medication is for you.

What's it for?

Olanzapine is licensed to treat the following conditions:

Taking olanzapine and sertraline: Elizabeth's story

Elizabeth tells her story of taking olanzapine and sertraline for anorexia.

Read Elizabeth's story

Name: olanzapine ("oh-LAN-za-peen")

Other names: Zyprexa® ("zi-PREX-a")

Medication type: atypical antipsychotic

What can it be used for?
If you are 18 or over, the doctor can prescribe olanzapine for you as a licensed medicine for mania, schizophrenia and bipolar disorder.

There is less research about its use and effectiveness in people under 18. Even so, specialists might prescribe it ‘off-label’ if they believe it is the best medicine for you.

Ways to take:
Tablets: 2.5mg, 5mg, 7.5mg, 10mg, 15mg, and 20mg strengths

Orodispersible tablets: 5mg, 10mg, 15mg and 20mg strengths (these may be called Zyprexa Velotabs®)

N.B. There are many companies making olanzapine tablets and the orodispersible ones. The non-active ingredients are likely to vary so if you have intolerances to certain sugars (e.g. lactose) or certain sweeteners (such as aspartame) then ask your pharmacist to check for you. If you need to avoid animal products such as gelatin, please note that this is often found in capsules but also in some tablet formulations. Ask your pharmacist if you have any questions about the ingredients.

Injections: 210mg, 300mg or 405mg in one injection (this may be called Zypadhera®)

How it works

What does olanzapine do?

There is a naturally-occurring chemical messenger ('neurotransmitter') in the brain called dopamine, which is mainly involved in thinking, emotions, behaviour and perception. With some illnesses, dopamine may be overactive, which upsets the normal balance of chemicals in the brain and can produce a variety of symptoms.

The main effect that olanzapine has is to block some dopamine receptors in the brain, correcting the overactivity of dopamine.

Olanzapine also has effects on other neurotransmitters in the brain such as serotonin (5-HT), which may also contribute to its beneficial effects.

How long does olanzapine take to start working?

It can take four to six weeks for olanzapine to show its full effects, but some studies show a good effect for some people within the first week of taking it.

You should stay in touch with your doctor to see how it goes over the first few weeks. They might do some tests to check your symptoms.

If you have had no good effects after two to three weeks, your doctor may increase the dose or change the medicine

Your doctor might start you on a low dose and then increase it slowly over two to four weeks to your full dose.

If you are starting on the long-acting injection (Zypadhera®), it can take a few days for the first injection to start working.

If you switch from olanzapine tablets to the injection, you may need to continue taking your tablets for the first few weeks after your first injection, as the injection takes a few weeks to kick in.

How long will I need to take olanzapine?

Many people take olanzapine for a few years.

How long you need to take it will depend on what condition you are taking it for.

You and your doctor should talk about how long you need to take olanzapine before you start your treatment.

If you stop the olanzapine, you will go back for checks to see that your old symptoms do not come back.

For psychosis or schizophrenia, if you have had one episode of illness, then it is best for you to keep taking olanzapine for at least two years to reduce the chances of becoming ill again. If you have had more than one episode of illness, then a period of at least five years is recommended.

If you are taking olanzapine to treat bipolar mania or bipolar depression, then you will need to discuss long-term medicines for your bipolar disorder with your doctor. This is to help stop the illness coming back.

For bipolar disorder, it is important to remain on medicines in the long term because every time you become ill, there is more chance of you becoming ill again. Olanzapine can be used as a long-term medicine, but there are other choices and lithium is still thought to be the best long-term medicine for bipolar disorder. You should discuss your options with your doctor.

For schizoaffective disorder, it is probably best to keep taking the olanzapine for several years to reduce the chances of the illness coming back. We know less about schizoaffective disorder, but it has some similarities to bipolar disorder and some similarities to schizophrenia.

Depression is usually treated with an antidepressant medicine, and olanzapine is sometimes added to an antidepressant for more severe depression. For people with severe depression, it is best to continue the antidepressant medicine for at least two years to stop the illness from coming back. The doctor is likely to recommend continuing olanzapine for the same length of time.

Taking olanzapine

You should only take olanzapine as agreed with your doctor.

You will get the best effect from olanzapine if you take it every day at the dose prescribed by your doctor.

Make sure that you know your dose. If it is not written on the label, check with your pharmacist or doctor.

You may start with a low dose that increases slowly to your regular dose over the next few days.

You will usually take your dose once a day.

It is usually recommended to take olanzapine at bedtime because it can cause sleepiness as a side effect.

However, it is important to choose a time of day to take it that you can easily remember, which could be bedtime, a mealtime, or when you brush your teeth.

You can take it before or after food.

For the plain-coated tablets, swallow them whole with a drink of water - if you chew them, they taste bitter.

Put orodispersible tablets (melts) on your tongue and let them dissolve there. You can also dissolve these in a glass of water, orange juice, apple juice or milk and then drink it all down.

A doctor or nurse can give you an injection in your bottom that provides a long-lasting dose of olanzapine, lasting for two or four weeks. You may need to take tablets alongside the injection, especially while the dose builds up. Every time you have the injection, you will be asked to wait at the centre for at least three hours so that they can check that the injection is not giving you too much olanzapine in one go. The good thing about a long-acting injection is that you don’t have to remember to take so many tablets every day. It is slowly working in your body all the time between injections.

What if I miss a dose?

If you remember later during the day, take it as soon as possible.

If you forget to take it by bedtime, just start again on the next day.

Do not take a double dose.

If it is less than 12 hours before your next dose of olanzapine, then do not take the missed dose because taking the doses too close together could cause more side effects.

If you miss your appointment for your injection, contact your doctor or nurse straight away to make another appointment.

It is very important to have the injection every two or four weeks.

What will happen if I forget to take my olanzapine?

If you forget to take your tablets for a while, or you miss an injection, you may start getting your old symptoms back. You should talk to your doctor if this happens.

Stopping the use of olanzapine

Once you start taking an antipsychotic, the brain adjusts to having a new level of dopamine around. If you stop taking the antipsychotic all at once, the balance starts to change again. You could get your old symptoms back.

Stopping this medicine quickly, or reducing the dose too much at once, may cause your old symptoms to come back, or cause you some withdrawal effects.

You can stop taking it safely with your doctor’s help.

People usually take olanzapine for a long time, to keep their symptoms away.

You may get your old symptoms back if you stop olanzapine for a while. You can also get withdrawal effects, including:

  • difficulty sleeping
  • feeling or being sick

It is better to agree stopping with a doctor who will reduce your dose gradually. This is likely to take a few weeks.

You will probably go for checks with your doctor after you stop olanzapine to check that you still feel better. 

The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.

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