Olanzapine: Complete Guide To Dosage, Side Effects, And Uses
Comprehensive guide to olanzapine: uses for schizophrenia, bipolar disorder, side effects, dosage, and important safety information.
About olanzapine tablets and liquid
Olanzapine belongs to a group of medicines called antipsychotics. These medicines are used to relieve the symptoms of schizophrenia and other similar mental health problems. Olanzapine may also have been prescribed for the treatment and/or prevention of high mood swings (mania) associated with bipolar disorder.
In schizophrenia, olanzapine works by blocking the effect of a chemical called dopamine in certain parts of the brain. Dopamine is involved in the symptoms of schizophrenia, which include hearing voices and delusions (feeling that others are working against you).
In mania, olanzapine works in a different way to stabilise mood. It interferes with communication between nerve cells in the brain by blocking the effect of dopamine and another chemical called serotonin. Serotonin is involved in regulating mood.
Key facts
- Olanzapine quickly starts to relieve symptoms such as restlessness and sleeping problems. It may take up to
six weeks
to relieve symptoms such as low mood, anxiety or poor concentration. - The usual starting dose for
schizophrenia
is 10 mg a day. Your dose may be increased up to a maximum of 20 mg a day. - The usual starting dose for
mania
is 15 mg a day. Your dose may be increased up to a maximum of 20 mg a day. - The most common side effects are feeling sleepy, dizziness, constipation and weight gain.
- Do not stop taking olanzapine suddenly as your symptoms may return.
About antipsychotics
Antipsychotic medicines do not cure illness but they can help to manage symptoms by balancing brain chemicals. There are two types of antipsychotics: typical and atypical. Olanzapine is an atypical antipsychotic (second-generation antipsychotic).
Atypical antipsychotics generally cause fewer movement problems than typical antipsychotics. However, they are more likely to cause weight gain and increase blood sugar and cholesterol levels.
How to take olanzapine
Before taking olanzapine
Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking olanzapine it is important that your doctor knows:
- If you are pregnant, trying for a baby or breastfeeding.
- If you have a heart condition, or a problem with your blood circulation or blood pressure.
- If you have epilepsy.
- If you have a condition that affects the way your liver works.
- If you have diabetes. Olanzapine can raise blood sugar levels.
- If you have had a stroke or have any problems with Parkinson’s disease.
- If you have high cholesterol levels.
- If you or your family have a history of blood clots.
- If you have any problems with the way your kidneys work.
- If you have ever had an allergic reaction to a medicine.
If you feel you have experienced an allergic reaction, inform your healthcare team.
How to take tablets or liquid
Take olanzapine exactly as your doctor tells you to. It is usual to be prescribed one dose a day, but your dose may be divided into two doses a day. Your doctor will tell you what dose to take. Dissolvable tablets should be placed on your tongue, allowed to dissolve and swallowed.
| Form | Dosage Guidance |
|---|---|
| Tablets | Swallow whole with water. Can be taken with or without food. |
| Orodispersible tablets | Place on tongue to dissolve. Do not chew. |
| Oral liquid | Use oral syringe provided. Shake bottle well. |
Your dose will be printed on the label of the pack of tablets or liquid to remind you about what the doctor said. It is important that you ask the question: ”What do I do if I miss a dose?”
If you forget to take olanzapine
- Take your dose as soon as you remember. If it is within 12 hours of your next dose, skip the missed dose and take the next dose as usual.
- Never take two doses together. Never take an extra dose to make up for a forgotten one.
If you take too much olanzapine
Contact your doctor or go to A&E straightaway. Take the medicine pack with you.
Can olanzapine cause problems?
Most people do not have problems but some people may get side effects. Many side effects resolve in time.
Common side effects
These side effects occur in more than 1 in 100 people. You can reduce some side effects by letting your body get used to the medicine.
| Side Effect | What to do |
|---|---|
| Feeling sleepy or unsteady | Avoid alcohol. Do not drive. Effects improve over time. |
| Dry mouth | Chew sugar-free gum. Drink plenty of water. |
| Constipation | Increase fibre, drink water, exercise. |
| Weight gain | Monitor weight. Eat healthily, exercise regularly. |
| Increased appetite | Choose healthy foods. Avoid sugary snacks. |
Serious side effects
Get medical help immediately if you have:
- Muscle stiffness or shaking (extrapyramidal symptoms).
- Fast/irregular heartbeat, dizziness (neuroleptic malignant syndrome).
- High temperature, stiff muscles (risk higher in hot weather).
- Difficulty swallowing or breathing.
- Yellowing of skin/eyes (liver problems).
- Swollen legs, pain/shortness of breath (blood clots).
- Changes in vision, especially after sunlight.
How to cope with side effects
Feeling sleepy: Take at night. Avoid alcohol. Rise slowly from sitting.
Weight gain: Olanzapine commonly causes weight gain due to increased appetite and metabolic changes. Regular monitoring of weight, blood sugar, and cholesterol is essential.
Off-label uses
Olanzapine is increasingly used off-label in palliative care for nausea, anxiety, insomnia, and cachexia. It antagonizes multiple receptors including dopamine and serotonin, making it versatile for symptom control.
- Chemotherapy-induced nausea: Doses of 5-10 mg effective in preventing CINV.
- Anxiety and insomnia: Low doses (2.5-5 mg) help manage these symptoms.
- Appetite stimulation: Useful in cachexia syndromes.
Caution is advised due to risks like sedation and metabolic effects, especially in frail patients.
Interactions with other medicines
Olanzapine can interact with:
- Medicines for Parkinson’s disease.
- Antidepressants, especially fluoxetine.
- Medicines that make you drowsy (alcohol, sleeping tablets).
- Carbamazepine (speeds up olanzapine clearance).
- Fluvoxamine (increases olanzapine levels).
Always inform your doctor of all medications.
Other medicines containing the same ingredient
Brand names: Zalasta®, Zyprexa®.
Long-acting injection
Maintenance doses can be given by depot injection (Zypadhera®) every 2-4 weeks for schizophrenia when tablets are not suitable.
Frequently asked questions
How long does olanzapine take to work?
Sleep improves within days. Full effects on mood and thoughts take 4-6 weeks.
Will olanzapine make me gain weight?
Yes, weight gain is common. Monitor diet and exercise.
Can I drink alcohol with olanzapine?
No. Alcohol increases drowsiness and dizziness.
Does olanzapine cause diabetes?
It can increase blood sugar. Diabetics need monitoring.
Can I stop olanzapine suddenly?
No. Taper under doctor supervision to avoid withdrawal.
Is olanzapine safe in pregnancy?
Not recommended. Discuss with your doctor.
What if I overdose?
Seek emergency help immediately.
Learn more
- Schizophrenia information
- Bipolar disorder leaflet
- Mental health support resources
References
- Benefits and risks of off-label olanzapine use for symptom management — APM. 2023. https://apm.amegroups.org/article/view/111460/html
- Olanzapine: Uses, Interactions, Mechanism of Action — DrugBank. 2024. https://go.drugbank.com/drugs/DB00334
- Olanzapine long-acting injection — Patient.info. 2023. https://patient.info/medicine/olanzapine-long-acting-injection-zypadhera
- Olanzapine for Nausea, Delirium, Anxiety, Insomnia and Cachexia — MyPCNow. 2019-03-04. https://www.mypcnow.org/fast-fact/olanzapine-for-nausea-delirium-anxiety-insomnia-and-cachexia/
- Olanzapine (Zalasta, Zyprexa) — Patient.info. 2023. https://patient.info/medicine/olanzapine-zalasta-zyprexa
- Olanzapine Pharmacokinetics: A Clinical Review — Dove Press. 2023. https://www.dovepress.com/olanzapine-pharmacokinetics-a-clinical-review-of-current-insights-and–peer-reviewed-fulltext-article-PGPM
- Olanzapine (Zyprexa) — NAMI. 2024. https://www.nami.org/treatments-and-approaches/mental-health-medications/types-of-medication/olanzapine-zyprexa/
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