HeadMeds gives young people in the United Kingdom general information about medication. HeadMeds does not give you medical advice. Please talk to your Doctor or anyone else who is supporting you about your own situation because everyone is different. Please read more important details about our site.

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Return to Olanzapine overview
  1. Use and Action
  2. Warnings and side effects
  3. Sex, drink, weight and everything else
Taking fluoxetine  haloperidol  diazepam  olanzapine video listing
Taking Fluoxetine, Haloperidol, Diazepam, Olanzapine
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Olanzapine can be used to treat the following conditions

Headmeds fills the medicines information gaps for young people - things you might want to know about meds like will it affect my sex life? Can I still study?  Can I drink?
Headmeds does not give medical advice so this is just general information.
Each medicine has a balance of good and bad effects, and each person gets their own individual effects.
You might want to know just one thing about your medicine, but on each page we have given you the ‘safety headlines’. Please read them as they are important.
We have included lots of information about each medicine - but if you want all the details, please look at the patient information leaflet - which is inside every pack. These leaflets are also at www.medicines.org.uk - where there will be the most up-to-date information.

Safety headlines

  • If you have taken more olanzapine than it said on the label, you must see a doctor quickly – even if you do not feel any different.
  • Olanzapine can sometimes cause serious side effects. Tell your doctor immediately if you experience unusual movements (mainly of the face or tongue). Go to hospital immediately if you think you may have developed a blood clot (symptoms are usually swelling, pain and redness in the leg); a clot may travel through blood vessels to the lungs causing chest pain and difficulty breathing. Also go to hospital if you develop a combination of fever, faster breathing, sweating, muscle stiffness or drowsiness; and tell them that you are taking olanzapine.
  • Stopping olanzapine suddenly can cause withdrawal effects, and stopping it too early could cause your illness to come back. See your doctor if you want to stop taking olanzapine because it is better to come off it gradually.
  • You might feel sleepy or dizzy in the first few days after taking olanzapine – do not drive a car, ride a bike or operate machines until you see how this affects you.
  • If you are pregnant, or thinking of becoming pregnant, please read the pregnancy section (see “Sex, drink, weight and everything else”) because olanzapine may affect the developing baby.

Basic details

The plain tablets contain lactose, the orodispersible tablets contain aspartame.

The Zyprexa brand of the orodispersible tablets also contain gelatine.

  • The plain coated olanzapine tablets may not be suitable for you if you have problems eating some sugars or dairy (milk-based) foods, as they contain lactose.
  • The olanzapine orodispersible (‘melt in your mouth’) tablets contain aspartame, which can be a problem for people who have a condition called phenylketonuria.
  • The Zyprexa brand of olanzapine orodispersible tablets also contain gelatin. Other manufacturers don’t include it.

How does olanzapine work?

  • There is a naturally occurring chemical messenger ('neurotransmitter') in the brain called dopamine.
  • Dopamine is the chemical messenger in the brain mainly involved with thinking, emotions, behaviour and perception.
  • In some illnesses, this dopamine may be overactive, which upsets the normal balance of chemicals in the brain.
  • This excess activity of dopamine produces some of the symptoms of the illness.
  • 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) receptors, which may also contribute to the beneficial effects of olanzapine.

You should take olanzapine as agreed with your doctor.

  • You will get the best effect from olanzapine if you take it regularly every day.
  • Make sure that you know your dose. If it is not written on the label, check it 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 your olanzapine dose at bedtime because olanzapine 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 tastes bitter.
  • For the orodispersible (‘melt in your mouth’) tablets, put it on your tongue and let it dissolve there. You can also dissolve it in a glass of water, orange juice, apple juice, milk or coffee and then drink it all down.
  • A doctor or nurse can use the long-acting injection in your bottom to give you a long lasting dose of olanzapine that lasts for 2 or 4 weeks – ask your doctor or nurse how often you have to come back.
  • You may have a tablet at the same time – under the supervision of a doctor.
  • The injection should change from the left buttock to the right side and switch each time, so it’s not in the same place all the time.
  • Every time you have the injection, you will be asked to wait at the centre for at least 3 hours so that they can check that the injection is not giving you too much olanzapine. Someone will check that you are OK before you leave.
  • The good thing about this is that you don’t have to remember to take your medicine every day. It is slowly working in your body all the time between injections.

What to do if you miss a dose of the tablets:

  • 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.

What to do if you miss an injection:

  • 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 2 or 4 weeks.

What might happen?

  • 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.

You must go to A&E if you take too much 

What to do if you take too much:

  • If you have taken more olanzapine than it said on the label, you must get help quickly – even if you do not feel any different.
  • Go to A&E. Take your medicine with you, to show to the doctors. Tell them how much you have taken.
  • Get a friend to go with you, if you can, just in case you feel ill on the way.

You might get any of the following signs:

  • rapid beating of the heart
  • agitation/aggressiveness
  • problems with speech
  • unusual movements (especially of the face or tongue)
  • reduced level of consciousness or coma
  • confusion
  • seizures (epilepsy)
  • a combination of fever, faster breathing, sweating, muscle stiffness and drowsiness or sleepiness, slower breathing, aspiration (breathing in vomit, mucus, or blood), high blood pressure or low blood pressure, and unusual rhythms of the heart.

It can take 4-6 weeks for olanzapine to show its full effect, but some people get good effects right from the first week.

  • Research evidence says that it takes 4-6 weeks for olanzapine to show its full effect.
  • Some studies now, however, show a good effect for some people within the first week of taking olanzapine.
  • 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 2-3 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 2-4 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 were already on olanzapine tablets, you may need to continue with them for the first few weeks on the injection, but you can start the injection on its own.

Many people take olanzapine for a few years.

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

  • How long you need to take olanzapine for depends on what condition you are taking it for. You should discuss how long you need to take it for with your doctor.
  • 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 have been taking olanzapine to treat bipolar mania or bipolar depression, then after a few weeks 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 a number of 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.

Reference sources

Search www.medicines.org.uk to find patient information leaflets and prescribing information on olanzapine. Plain tablets, orodisperible tablets and injection are listed separately and the original brand is Zyprexa but there are many other manufacturers. The SmPC lists all the inactive ingredients in the product so you can check against any allergies. If you are still unsure about this then speak to your pharmacist.

  • British National Formulary (BNF) and British National Formulary for children. Download the BNF/BNFC app (blue background) on to your mobile device. No longer available for public access via the web 
  • Taylor D, Barnes T, Young A. Maudsley Prescribing Guidelines in Psychiatry, 13th edition. Oxford: John Wiley & Sons, May 2018. ISBN: 978-1-119-44260-8
  • Royal Pharmaceutical Society. Medicines Ethics and Practice (42nd edition). London: RPS, 2018. Standards for pharmacists to work to. It is not a free publication
  • World Anti Doping Agency WADA Prohibited List https://www.wada-ama.org/en/resources/science-medicine/prohibited-list-documents 
  • Choiceandmedication; an independent source of information on many mental health conditions and their medicines with easy to read fact sheets www.choiceandmedication.org Personal subscriptions to download the app available for £1 per month (with proportionate discounts for longer periods) but your local mental health Trust may subscribe and provide information sheets for free.
  • Best Use of Medicines in Pregnancy (BUMPS). Information sheets on drugs in pregnancy http://www.medicinesinpregnancy.org/ 
  • Drugs and Lactation Database (LactMed). Information on drugs in breastfeeding https://toxnet.nlm.nih.gov/newtoxnet/lactmed.htm
  • NICE CG178 Psychosis and Schizophrenia in adults. Updated March 2014. Available online https://www.nice.org.uk/guidance/cg178
  • NICE CG155 Psychosis and schizophrenia in children and young people. Updated October 2016. Available online https://www.nice.org.uk/guidance/cg155
  • NICE CG185 Bipolar disorder: assessment and management. Updated April 2018. Available online https://www.nice.org.uk/guidance/cg185