An atypical (second-generation) antipsychotic
Olanzapine
An effective atypical antipsychotic for schizophrenia and bipolar disorder, well known for causing weight gain and metabolic changes that need regular monitoring.
What is Olanzapine?
Olanzapine is a widely used atypical, or second-generation, antipsychotic. It is taken for schizophrenia and for the manic or mixed phases of bipolar disorder, and sometimes to help prevent these episodes returning.
Education and reference only. This is a plain-language guide to Olanzapine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Olanzapine is a widely used atypical (second-generation) antipsychotic, taken for schizophrenia and for the manic or mixed phases of bipolar disorder, and sometimes to keep bipolar disorder stable. It is generally effective and often quite calming, which can help with agitation and sleep. Its best-known drawback is its effect on the body's metabolism: it commonly causes weight gain and can raise blood sugar and blood fats, so its benefits are weighed against these effects and monitored over time.
How it works
Many symptoms of psychosis and mania are linked to overactivity of the brain chemical dopamine, and to the signalling of serotonin. Olanzapine works mainly by blocking certain dopamine receptors, which dampens the hallucinations, delusions and disordered thinking of psychosis, alongside blocking serotonin and other receptors that contribute to its calming effect. Its action on histamine and other receptors helps explain both its sedating quality and its tendency to increase appetite and weight.
Company & origin
Originated / developed by: Eli Lilly.
Olanzapine, an atypical antipsychotic, was developed by Eli Lilly and Company (USA) and first approved by the US FDA in 1996, marketed as Zyprexa.
What it treats
Conditions Olanzapine is used for
Practical use
How to take Olanzapine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Usually taken once a day, often in the evening, as it can be sedating.
- Can be taken with or without food at a regular time.
- Keep taking it even when you feel better, as stopping can lead to a relapse.
- Do not stop suddenly without medical advice.
- Attend appointments for weight, blood sugar and cholesterol checks, as these can be affected.
- Avoid much alcohol, which adds to drowsiness.
Weighing it up
Advantages & disadvantages of Olanzapine
Advantages
- Effective for schizophrenia and the manic phase of bipolar disorder.
- Taken once daily.
- Well-established medicine with extensive clinical experience.
Disadvantages
- Often causes weight gain and can raise blood sugar and cholesterol, requiring monitoring.
- Can cause significant drowsiness.
- Needs regular metabolic monitoring during treatment.
- Should not be stopped abruptly because of the risk of relapse.
Practical use
Good to know
It is taken regularly, usually once a day, and is often taken in the evening because it can be sedating. It should not be stopped suddenly: stopping abruptly can cause the illness to return or rebound symptoms, so any change is made gradually and with support. Weight, waist size, blood sugar and blood fats are checked before starting and at intervals afterwards, and lifestyle support is offered early. Because it can cause drowsiness, care is needed with driving until you know how it affects you, and alcohol adds to the sedation.
Who should not take it / use with caution
- Older people with dementia should generally not take it for behavioural symptoms, as antipsychotics raise the risk of stroke and death in this group.
- Used with great caution in people with diabetes or a strong tendency to it, significant heart disease, or a history of low white-blood-cell counts.
- Caution in significant liver disease, in people prone to seizures, in Parkinson's disease, and in pregnancy or breastfeeding, where the decision is balanced individually.
Monitoring
- Weight, waist measurement, blood sugar (including HbA1c) and blood fats before starting and regularly
- Blood pressure and pulse
- Mental state, side effects and, in some cases, blood counts
Side effects
- Weight gain and increased appetite are common and often substantial; raised blood sugar and blood fats can develop.
- Drowsiness, dizziness (especially on standing), dry mouth and constipation.
- Less commonly, movement effects (stiffness, tremor or restlessness), and rarely serious problems such as a dangerous reaction with fever and rigidity (neuroleptic malignant syndrome) or a sharp drop in protective white blood cells — report high fever, severe stiffness or signs of infection.
Key interactions
- Other sedating medicines, opioids and alcohol add to drowsiness.
- Smoking lowers its levels, so stopping or starting smoking can change how much effect it has and may need a review.
- Care alongside medicines for Parkinson's disease (it can oppose them) and with other medicines that affect the heart's rhythm.
Available as: Tablets, orodispersible tablets that melt on the tongue, and a long-acting injection given in a clinical setting.
Answers
Olanzapine: frequently asked questions
Will olanzapine make me put on weight?
It commonly does, and the gain can be significant, partly because it increases appetite. This is why weight, blood sugar and blood fats are checked before starting and monitored over time, and why diet and activity support is offered early. If weight gain becomes a problem, discuss it — sometimes a different antipsychotic is considered.
Can I stop taking it once I feel well?
Don't stop suddenly or on your own. Stopping abruptly can bring the illness back or cause rebound symptoms, and the timing of any change matters. If you want to come off it, your prescriber can reduce it gradually with support and a plan to watch for early warning signs.
Why does it make me so sleepy?
Olanzapine blocks histamine and other receptors, which makes it quite sedating — sometimes a useful effect for agitation or poor sleep. It is often taken in the evening for this reason. Drowsiness usually eases over the first weeks; until it does, take care with driving and avoid alcohol.
Does smoking affect my olanzapine?
Yes. Tobacco smoke speeds up how the body clears olanzapine, so smokers may have lower levels. If you start or stop smoking (including going into hospital where you can't smoke), tell your prescriber, as the amount you need may change.
What is the difference between olanzapine and Zyprexa?
They are the same medicine — olanzapine is the generic (active-ingredient) name and Zyprexa is the brand. Generic olanzapine contains the identical active ingredient and works the same way; it is usually cheaper.
The wider class
About Antipsychotics
Olanzapine belongs to the antipsychotics class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Olanzapine.
- electronic Medicines Compendium (SmPC): Olanzapine (Zyprexa).
- NICE: Psychosis and schizophrenia in adults.
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