Olanzapine: Uses, Dosage & Side Effects
Atypical antipsychotic for schizophrenia and bipolar disorder
Quick Facts About Olanzapine
Key Takeaways About Olanzapine
- Primary indications: Olanzapine treats schizophrenia and moderate-to-severe manic episodes in bipolar disorder, and prevents recurrence of mania
- Metabolic monitoring is essential: Weight gain, elevated blood sugar, and raised cholesterol are common — regular blood tests and weight checks are critical
- Do not stop suddenly: Abrupt discontinuation may cause withdrawal symptoms including insomnia, sweating, tremor, and nausea
- Not for elderly with dementia: Olanzapine is not recommended in elderly patients with dementia due to increased risk of stroke and death
- Takes 2–4 weeks for full effect: Sedation occurs quickly, but the full antipsychotic effect develops over several weeks
What Is Olanzapine and What Is It Used For?
Olanzapine is an atypical (second-generation) antipsychotic that modulates dopamine and serotonin signalling in the brain. It is primarily prescribed for schizophrenia and moderate-to-severe manic episodes in bipolar disorder, and helps prevent recurrence of mania in patients who respond to initial treatment.
Olanzapine belongs to the thienobenzodiazepine class of atypical antipsychotics and is one of the most widely prescribed medications for serious mental health conditions worldwide. It is listed on the WHO Model List of Essential Medicines, reflecting its importance in global healthcare. Unlike older (first-generation) antipsychotics that primarily block dopamine receptors, olanzapine acts on multiple neurotransmitter systems simultaneously.
The medication works by blocking several types of receptors in the brain, including dopamine D1–D4 receptors, serotonin 5-HT2A and 5-HT2C receptors, muscarinic receptors, histamine H1 receptors, and alpha-1 adrenergic receptors. This broad receptor profile contributes to its effectiveness against both the positive symptoms of psychosis (hallucinations, delusions, disorganised speech) and the negative symptoms (social withdrawal, flat affect, reduced motivation).
Schizophrenia
Schizophrenia is a chronic psychiatric condition characterised by symptoms such as hearing, seeing, or sensing things that are not there (hallucinations), holding fixed false beliefs (delusions), unusual suspiciousness, and social withdrawal. People with schizophrenia may also experience depression, anxiety, and tension. Olanzapine helps manage these symptoms by restoring the balance of neurotransmitter activity in the brain. Clinical evidence from large-scale meta-analyses, including a landmark 2019 Lancet study comparing 32 antipsychotics, demonstrates that olanzapine is among the most effective medications for treating acute schizophrenia episodes.
Bipolar disorder — manic episodes
Bipolar disorder involves extreme mood swings between manic episodes (periods of elevated mood, excessive energy, reduced need for sleep, and impulsive behaviour) and depressive episodes. Olanzapine is used to treat moderate to severe manic episodes. It can rapidly reduce agitation, racing thoughts, and grandiosity associated with mania. Furthermore, olanzapine is effective as maintenance therapy to prevent recurrence of manic episodes in patients who responded well to the medication during the acute phase.
Olanzapine should always be used under the supervision of a psychiatrist or other specialist experienced in treating serious mental health conditions. The decision to start, adjust, or stop olanzapine should be made jointly between patient and clinician, considering the balance of benefits and risks for each individual.
What Should You Know Before Taking Olanzapine?
Before starting olanzapine, inform your doctor about all existing medical conditions, current medications, and whether you are pregnant or breastfeeding. Olanzapine has important contraindications, warnings, and interactions that must be considered to ensure safe and effective treatment.
Olanzapine is a potent medication that affects several organ systems beyond the brain. Before starting treatment, your doctor will need a comprehensive picture of your health to minimise risks. This includes baseline measurements of your weight, blood glucose, lipid profile (cholesterol and triglycerides), and blood pressure. These values will be monitored at regular intervals throughout treatment.
Contraindications
You should not take olanzapine if you have a known allergy (hypersensitivity) to olanzapine or any of the other ingredients in the formulation. An allergic reaction may present as skin rash, itching, swelling of the face or lips, or difficulty breathing. If any of these symptoms occur, contact your doctor immediately.
Olanzapine is also contraindicated in patients with known risk of narrow-angle glaucoma (increased pressure in the eye). If you have been diagnosed with or are at risk for this condition, discuss alternative medications with your doctor.
Warnings and precautions
There are several important medical conditions and risk factors that your doctor needs to be aware of before prescribing olanzapine:
Olanzapine is not recommended for use in elderly patients with dementia-related psychosis. Studies have shown an increased risk of stroke, pneumonia, urinary incontinence, falls, elevated body temperature, skin redness, gait difficulties, extreme fatigue, and death in this population. If you are caring for an elderly person with dementia, discuss safer alternatives with their doctor.
Tell your doctor if you have or have ever had any of the following conditions:
- Stroke or transient ischaemic attack (TIA) — olanzapine may increase cerebrovascular risk
- Parkinson's disease — olanzapine may worsen Parkinsonian symptoms
- Diabetes mellitus — olanzapine can significantly raise blood glucose levels
- Heart disease — including arrhythmias, heart failure, or recent myocardial infarction
- Liver or kidney disease — dose adjustments may be necessary
- Epilepsy or seizure history — olanzapine can lower the seizure threshold
- Prostate problems — urinary retention may occur
- Bowel obstruction (paralytic ileus)
- Blood disorders — olanzapine may affect white blood cell counts
- History of blood clots (venous thromboembolism) — antipsychotics have been associated with increased clotting risk
Patients over 65 years of age should have their blood pressure monitored regularly during treatment, as olanzapine can cause orthostatic hypotension (a drop in blood pressure when standing up), which increases the risk of falls.
Olanzapine carries a significant risk of causing metabolic syndrome, including weight gain, high blood sugar (hyperglycaemia), and elevated blood fats (dyslipidaemia). Your doctor should test your blood glucose and lipid levels before starting olanzapine and at regular intervals during treatment. Referral to a dietitian or provision of dietary advice may be recommended. Regular physical activity is encouraged throughout treatment.
Children and adolescents
Olanzapine is not intended for use in patients under 18 years of age. Clinical data on the safety and efficacy of olanzapine in children and adolescents is limited, and the metabolic side effects (weight gain, glucose and lipid changes) may be more pronounced in younger patients. If an antipsychotic is needed for a child or adolescent, the prescribing doctor will consider age-appropriate alternatives.
Pregnancy and breastfeeding
If you are pregnant, think you may be pregnant, or are planning to become pregnant, consult your doctor before taking olanzapine. The medication should only be used during pregnancy if the potential benefits clearly outweigh the risks to the foetus. Olanzapine is not a known teratogen, but limited data are available from controlled studies in pregnant women.
Newborns whose mothers took olanzapine during the third trimester may experience withdrawal symptoms including tremor, muscle stiffness or weakness, sleepiness, agitation, breathing difficulties, and feeding problems. If your baby develops any of these symptoms after birth, contact your doctor promptly.
Small amounts of olanzapine pass into breast milk. Breastfeeding is not recommended during olanzapine treatment. Discuss alternative feeding methods with your doctor if you need to continue the medication while caring for a newborn.
Driving and operating machinery
Olanzapine can cause drowsiness, dizziness, and blurred vision, particularly during the initial phase of treatment or after dose increases. Do not drive or operate heavy machinery until you know how olanzapine affects you. If drowsiness persists, discuss this with your doctor as dose adjustment or timing changes may help.
How Does Olanzapine Interact with Other Drugs?
Olanzapine interacts with several medications that can increase or decrease its effects. Key interactions include carbamazepine (which decreases olanzapine levels), fluvoxamine and ciprofloxacin (which increase olanzapine levels), and central nervous system depressants including alcohol. Always inform your doctor of all medications you take.
Drug interactions with olanzapine can occur through several mechanisms, including effects on liver enzymes (particularly CYP1A2 and CYP2D6) that metabolise olanzapine, and additive pharmacological effects on the central nervous system. It is crucial that your doctor and pharmacist are aware of all medications you are taking, including prescription drugs, over-the-counter medicines, and herbal supplements.
Major interactions
The following interactions are clinically significant and may require dose adjustments or close monitoring:
| Drug | Effect | Mechanism | Action Required |
|---|---|---|---|
| Carbamazepine | Decreases olanzapine levels | CYP1A2 induction | Olanzapine dose increase may be needed |
| Fluvoxamine | Increases olanzapine levels significantly | CYP1A2 inhibition | Olanzapine dose reduction required |
| Ciprofloxacin | Increases olanzapine levels | CYP1A2 inhibition | Monitor closely; dose adjustment may be needed |
| Levodopa / Dopamine agonists | Mutual antagonism | Opposing effects on dopamine receptors | May worsen Parkinson's symptoms; avoid if possible |
| Benzodiazepines | Additive sedation, respiratory depression risk | CNS depression | Use with caution; monitor for excessive sedation |
Other notable interactions
Alcohol: Do not consume alcohol while taking olanzapine. The combination can cause excessive drowsiness, impaired judgement, and respiratory depression. Alcohol can worsen many of the side effects of olanzapine.
Antidepressants and anxiolytics: Taking olanzapine together with certain antidepressants or anti-anxiety medications may increase sedation. Your doctor may adjust the doses of either medication to minimise this effect.
Antihypertensives: Olanzapine can lower blood pressure. When combined with blood pressure medications, excessive hypotension may occur. Blood pressure monitoring is recommended, especially during the first weeks of combined treatment.
Smoking: Tobacco smoking induces CYP1A2, which metabolises olanzapine. Patients who smoke may require higher doses of olanzapine. Conversely, if you stop smoking during treatment, olanzapine levels may rise and your doctor may need to reduce the dose.
What Is the Correct Dosage of Olanzapine?
The typical adult dose of olanzapine ranges from 5 mg to 20 mg taken once daily. The starting dose depends on the condition being treated, and adjustments are made based on clinical response and tolerability. Always take olanzapine exactly as prescribed by your doctor.
The dose of olanzapine is individualised by your prescribing doctor based on your specific condition, symptom severity, age, other medications, and overall health. Olanzapine should be taken once daily, at the same time each day, with or without food. Treatment duration is determined by your doctor and may be long-term for chronic conditions such as schizophrenia.
Adults
| Indication | Starting Dose | Usual Range | Maximum Dose |
|---|---|---|---|
| Schizophrenia | 10 mg/day | 5–20 mg/day | 20 mg/day |
| Acute mania (bipolar) | 15 mg/day (monotherapy) | 5–20 mg/day | 20 mg/day |
| Bipolar maintenance | 10 mg/day | 5–20 mg/day | 20 mg/day |
Dose adjustments should be made at intervals of no less than 24 hours, typically in increments of 5 mg. Your doctor will aim to find the lowest effective dose that controls your symptoms while minimising side effects.
Elderly patients
A lower starting dose of 5 mg/day may be considered for elderly patients, particularly those over 65 years. Dose increases should be made more cautiously, with careful monitoring for orthostatic hypotension, sedation, and falls. As noted above, olanzapine is not recommended for elderly patients with dementia-related psychosis.
Patients with liver or kidney impairment
A lower starting dose of 5 mg/day should be considered for patients with moderate hepatic (liver) impairment. Dose escalation should be cautious. Olanzapine has not been studied in patients with severe hepatic impairment. Renal (kidney) impairment does not generally require dose adjustment, but lower starting doses and careful titration are prudent.
How to take orodispersible tablets
Orodispersible (mouth-dissolving) tablets are designed to dissolve on the tongue and should be handled with care:
- Handle the tablet with dry hands — moisture can cause premature dissolution
- Peel apart the blister foil carefully; do not push the tablet through the foil
- Place the tablet on your tongue immediately after removal from the packaging
- The tablet will dissolve within seconds and can be swallowed with or without water
- Ensure your mouth is empty before placing the tablet on your tongue
Alternatively, the orodispersible tablet may be dissolved in a glass of water and drunk immediately.
Missed dose
If you forget to take your olanzapine, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular schedule. Do not take a double dose to make up for a forgotten one.
Overdose
Symptoms of olanzapine overdose may include rapid heart rate, agitation or aggression, speech difficulties, involuntary movements (especially of the face or tongue), reduced consciousness, confusion, seizures, coma, fever, rapid or slow breathing, respiratory depression, abnormally high or low blood pressure, and abnormal heart rhythm. If you suspect an overdose, call your local emergency number immediately and bring any remaining tablets with you to the hospital.
What Are the Side Effects of Olanzapine?
Like all medications, olanzapine can cause side effects, though not everyone experiences them. The most common side effects include weight gain, drowsiness, and increased prolactin levels. Serious but rare effects include neuroleptic malignant syndrome (NMS), tardive dyskinesia, and venous thromboembolism. Report any concerning symptoms to your doctor.
Side effects of olanzapine can range from mild and temporary to serious and potentially life-threatening. The metabolic effects (weight gain, blood sugar changes, lipid changes) are among the most clinically significant and require ongoing monitoring. Many of the common side effects, such as drowsiness and dizziness, tend to be most pronounced at the start of treatment and may improve over time.
Neuroleptic malignant syndrome (NMS): A rare but potentially fatal combination of high fever, rapid breathing, sweating, muscle rigidity, and drowsiness or confusion. Tardive dyskinesia: Involuntary, repetitive movements especially of the face or tongue. Blood clots: Swelling, pain, or redness in the leg, chest pain, or sudden difficulty breathing.
Very Common
- Weight gain (often significant)
- Drowsiness and somnolence
- Elevated prolactin levels
- Orthostatic dizziness (especially when standing up, at start of treatment)
Common
- Increased appetite
- Elevated blood glucose and cholesterol levels
- Elevated triglycerides
- Temporarily elevated liver enzymes
- Increased uric acid and creatine phosphokinase
- Dizziness, restlessness (akathisia)
- Tremor and movement difficulties (dyskinesia)
- Constipation, dry mouth
- Skin rash
- Weakness, extreme fatigue
- Fluid retention (swelling in hands, ankles, or feet)
- Fever, joint pain
- Sexual dysfunction (decreased libido, erectile dysfunction)
Uncommon
- Hypersensitivity reactions (swelling of mouth/throat, itching, rash)
- Diabetes or worsening of existing diabetes, potentially with ketoacidosis
- Seizures (especially in those with a history of epilepsy)
- Muscle rigidity or spasms (including eye movements)
- Restless legs syndrome
- Speech difficulties, stuttering
- Slow heartbeat (bradycardia)
- Photosensitivity (increased sensitivity to sunlight)
- Nosebleeds, abdominal bloating, drooling
- Memory loss or forgetfulness
- Urinary incontinence, difficulty urinating
- Hair loss
- Absent or shortened menstrual periods
- Breast changes (abnormal breast milk production, breast enlargement)
Rare
- Lowered body temperature (hypothermia)
- Abnormal heart rhythm
- Pancreatitis (severe abdominal pain, fever, nausea)
- Liver disease (jaundice — yellowing of skin and eyes)
- Rhabdomyolysis (muscle disease with unexplained pain)
- Prolonged and/or painful erection (priapism)
Very Rare
- Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) — a serious allergic reaction with flu-like symptoms, rash, fever, swollen lymph nodes, and elevated liver enzymes
Patients with Parkinson's disease
Olanzapine may worsen the motor symptoms of Parkinson's disease. If you have Parkinson's disease and are prescribed olanzapine, your doctor will monitor you closely for any deterioration of your Parkinsonian symptoms. In many cases, alternative antipsychotics with a lower risk of extrapyramidal effects will be preferred.
It is important to report any suspected side effects to your healthcare provider. You can also report side effects directly to your national pharmacovigilance authority (e.g., the FDA MedWatch programme in the US, the Yellow Card Scheme in the UK, or the EMA's EudraVigilance system in the EU). Reporting helps ensure ongoing monitoring of the benefit-risk balance of medications.
What Happens If You Stop Taking Olanzapine?
Do not stop olanzapine abruptly. Sudden discontinuation can cause withdrawal symptoms including sweating, insomnia, tremor, anxiety, nausea, and vomiting. Your doctor will recommend a gradual dose reduction when it is appropriate to stop treatment.
It is essential that you continue taking olanzapine as prescribed by your doctor, even if you feel better. Many psychiatric conditions are chronic in nature, and stopping medication prematurely significantly increases the risk of relapse. Studies show that patients with schizophrenia who discontinue antipsychotic treatment have relapse rates of 60–80% within a year, compared to 20–30% for those who continue maintenance therapy.
If you and your doctor decide to discontinue olanzapine, the dose should be reduced gradually over several weeks rather than stopped suddenly. Abrupt cessation may cause discontinuation symptoms including:
- Excessive sweating
- Difficulty sleeping (insomnia)
- Tremor and shaking
- Anxiety and irritability
- Nausea and vomiting
- Rebound psychotic symptoms
Your doctor will create a tapering schedule tailored to your situation, typically reducing the dose by small increments every 1–2 weeks while monitoring for any return of symptoms or withdrawal effects.
How Should You Store Olanzapine?
Store olanzapine in its original packaging, away from light and moisture, at room temperature. Keep out of reach of children. Do not use after the expiry date printed on the packaging.
Proper storage of olanzapine helps ensure the medication remains effective and safe throughout its shelf life. Follow these storage guidelines:
- Keep in original packaging — the blister pack or bottle protects the tablets from light and moisture
- Store at room temperature — no special temperature requirements, but avoid extreme heat or cold
- Protect from light — do not remove tablets from the blister pack until ready to take
- Protect from moisture — especially important for orodispersible tablets, which dissolve on contact with water
- Keep out of sight and reach of children
- Check the expiry date — do not use olanzapine after the date shown on the packaging; the expiry date refers to the last day of that month
Do not dispose of medications via household waste or down the drain. Return unused or expired olanzapine to your pharmacist for safe disposal. This helps protect the environment and prevent accidental exposure.
What Does Olanzapine Contain?
The active ingredient is olanzapine. Tablets are available in strengths of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg, and 20 mg. The inactive ingredients (excipients) vary by formulation but commonly include mannitol, microcrystalline cellulose, and magnesium stearate.
Each olanzapine tablet or orodispersible tablet contains the active ingredient olanzapine in the dose specified on the packaging. The inactive ingredients serve various pharmaceutical purposes such as binding, filling, and enabling dissolution of the tablet.
Common excipients in olanzapine formulations
- Mannitol — sweetener and bulking agent
- Microcrystalline cellulose — binder and filler
- Crospovidone — disintegrant (helps the tablet break apart)
- Low-substituted hydroxypropyl cellulose — binder
- Magnesium stearate — lubricant for manufacturing
- Calcium silicate — flow agent
Some orodispersible formulations of olanzapine contain aspartam, which is a source of phenylalanine. This may be harmful for people with phenylketonuria (PKU), a rare inherited condition that leads to accumulation of high levels of phenylalanine in the body. Check the package leaflet of your specific product or ask your pharmacist if you have PKU.
Olanzapine is available under numerous brand names worldwide, including Zyprexa (the original brand), Zalasta, Olanzapine Actavis, Olanzapine SUN, Olanzapine Accord, Olanzapine Viatris, Olanzapine Glenmark, and Olanzapine Sandoz, among others. All approved generic versions must demonstrate bioequivalence to the original product to receive marketing authorisation.
Frequently Asked Questions About Olanzapine
Olanzapine is an atypical antipsychotic medication used to treat schizophrenia and moderate-to-severe manic episodes in bipolar disorder. It helps manage symptoms such as hallucinations, delusions, disorganised thinking, and severe mood swings. It is also used as maintenance therapy in bipolar disorder to prevent recurrence of manic episodes in patients who responded to initial olanzapine treatment.
The most common side effects (affecting more than 1 in 10 people) include weight gain, increased appetite, drowsiness/somnolence, elevated prolactin levels, and orthostatic hypotension (dizziness when standing up). Olanzapine is particularly associated with significant metabolic effects including raised blood sugar levels, increased cholesterol and triglycerides. Regular monitoring of weight, blood glucose, and lipid levels is essential during treatment.
No, you should not stop taking olanzapine suddenly without medical supervision. Abruptly discontinuing olanzapine can cause withdrawal symptoms including sweating, insomnia, tremor, anxiety, nausea, and vomiting. Your doctor will usually recommend gradually reducing the dose over time. Always consult your doctor before making any changes to your medication.
Yes, weight gain is one of the most common side effects of olanzapine. Studies show that significant weight gain occurs in a majority of patients, with some gaining 7% or more of their initial body weight. This is more pronounced than with many other antipsychotics. Regular weight monitoring, dietary counselling, and physical activity are recommended throughout treatment. Your doctor may consider switching medications if weight gain becomes excessive.
Olanzapine should only be used during pregnancy if the potential benefit justifies the potential risk to the foetus. Newborns exposed to antipsychotics during the third trimester may experience withdrawal symptoms including tremor, muscle stiffness, weakness, sleepiness, agitation, breathing problems, and feeding difficulties. Women who are pregnant or planning to become pregnant should discuss the risks and benefits with their doctor. Olanzapine passes into breast milk, so breastfeeding is not recommended during treatment.
Some effects of olanzapine, particularly sedation and calming effects, may be noticed within hours to days. However, the full antipsychotic effect typically takes 2 to 4 weeks to develop, and for some patients it may take 6 to 8 weeks. It is important to continue taking the medication as prescribed even if you do not notice immediate improvement. Do not stop taking olanzapine without consulting your doctor.
References
- World Health Organization. WHO Model List of Essential Medicines — 23rd List (2023). Geneva: WHO; 2023. Available from: who.int
- European Medicines Agency. Zyprexa (olanzapine) — Summary of Product Characteristics. EMA; 2024. Available from: ema.europa.eu
- U.S. Food and Drug Administration. Zyprexa (olanzapine) Prescribing Information. FDA; 2024.
- Huhn M, Nikolakopoulou A, Schneider-Thoma J, et al. Comparative efficacy and tolerability of 32 oral antipsychotics for the acute treatment of adults with multi-episode schizophrenia: a systematic review and network meta-analysis. Lancet. 2019;394(10202):939–951. doi:10.1016/S0140-6736(19)31135-3
- National Institute for Health and Care Excellence. Psychosis and schizophrenia in adults: prevention and management (CG178). NICE; 2024.
- British National Formulary. Olanzapine. BNF; 2024. Available from: bnf.nice.org.uk
- Leucht S, Cipriani A, Spineli L, et al. Comparative efficacy and tolerability of 15 antipsychotic drugs in schizophrenia: a multiple-treatments meta-analysis. Lancet. 2013;382(9896):951–962.
- American Psychiatric Association. Practice Guideline for the Treatment of Patients with Schizophrenia. 3rd ed. APA; 2021.
- Correll CU, Solmi M, Croatto G, et al. Mortality in people with schizophrenia: a systematic review and meta-analysis of studies. World Psychiatry. 2022;21(2):304–317.
- Taylor DM, Barnes TRE, Young AH. The Maudsley Prescribing Guidelines in Psychiatry. 14th ed. Wiley-Blackwell; 2021.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, comprising licensed specialist physicians in clinical pharmacology and psychiatry. Our editorial process follows the GRADE evidence framework and adheres to international medical guidelines from the WHO, EMA, FDA, NICE, and APA.
Content developed by medical professionals with expertise in pharmacology and psychiatric medicine, following evidence-based medicine principles.
Independently reviewed by the iMedic Medical Review Board to ensure accuracy, completeness, and adherence to current clinical guidelines.
All medical claims are supported by Level 1A evidence (systematic reviews and meta-analyses of randomised controlled trials) where available.
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