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[Pharmacology](https://durgical.com/en/pharmacology/) · [Second-generation antipsychotics](https://durgical.com/en/pharmacology/classes/second-generation-antipsychotics/)

# Olanzapine

An atypical antipsychotic for schizophrenia and bipolar mania; effective but with one of the highest risks of weight gain and diabetes.

Updated 2026-11-01

- Class: [Second-generation antipsychotics](https://durgical.com/en/pharmacology/classes/second-generation-antipsychotics/)
- Receptor: Dopamine D2 receptor
- ATC code: N05AH03
- WHO Model List of Essential Medicines

◎**Dopamine D2 receptor**Olanzapine

ⓘ The figure shows risperidone in the human D2 receptor; olanzapine blocks the same site (no olanzapine-bound D2 structure exists).

**Target in 3D:** Dopamine D2 receptor. PDB structure 6CM4 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/6CM4) · Drag to rotate · pinch to zoom

## Mechanism of action

Olanzapine blocks D2 and 5-HT2A receptors, and also H1, 5-HT2C and muscarinic receptors. The H1 and 5-HT2C blockade increase appetite and explain the marked weight gain and metabolic effects; muscarinic blockade gives anticholinergic effects.

- Olanzapine blocks D2 and 5-HT2A receptors
- Psychotic and manic symptoms improve
- H1 and 5-HT2C block: more appetite and weight gain
- Insulin resistance: high glucose and lipids

## Pharmacokinetics

**Absorption**
Taken by mouth (also orally disintegrating tablets) or by intramuscular injection

**Metabolism**
Liver, partly by CYP1A2; smokers clear it faster, and carbamazepine speeds clearance

## Indications

- Schizophrenia
- Manic or mixed episodes of bipolar I disorder, and maintenance
- Acute agitation in schizophrenia or bipolar mania (intramuscular form)
- Bipolar depression, combined with fluoxetine

## Adverse effects

### Common

- Weight gain and increased appetite
- Sedation and dizziness
- Dry mouth and constipation
- Raised prolactin (less than risperidone)

### Serious (rare, important)

- Hyperglycaemia and diabetes, sometimes with ketoacidosis
- Dyslipidaemia
- DRESS (drug reaction with eosinophilia and systemic symptoms), sometimes fatal
- Neuroleptic malignant syndrome
- Tardive dyskinesia (may be irreversible)
- Higher mortality in older people with dementia-related psychosis (boxed warning)

## Contraindications

- Hypersensitivity to olanzapine

## Key interactions

**Parenteral benzodiazepines (with intramuscular olanzapine)**
Excessive sedation and cardiorespiratory depression: not recommended together

**Fluvoxamine**
Higher olanzapine levels (CYP1A2 inhibition)

**Carbamazepine or smoking**
Faster clearance and lower levels (CYP1A2 induction)

**Other anticholinergic drugs**
Higher risk of severe constipation and ileus

## What is monitored

- Weight, BMI and waist
- Fasting glucose or HbA1c and lipids
- Abnormal movements
- Rash with fever or swollen glands (DRESS)

## Administration and safety

- Intramuscular olanzapine is not combined with parenteral benzodiazepines
- After an intramuscular dose, sedation, blood pressure and breathing are watched
- Look-alike names: olanzapine and quetiapine are both antipsychotics with similar names; the label is read carefully

## Nursing care

- Records weight, waist, glucose and lipids at baseline and during treatment
- Teaches the signs of high glucose: thirst, frequent urination, hunger, weakness
- Encourages diet and physical activity from the start
- Watches for fever, rigidity and confusion (neuroleptic malignant syndrome) and for abnormal movements; reports them at once

## Pregnancy and breastfeeding

Newborns exposed in the third trimester may have extrapyramidal or withdrawal symptoms (agitation, abnormal tone, tremor, feeding problems); use weighs benefit and risk.

## Memory aid

«OLANZapine: O for Obesity»: the strongest appetite of the atypicals after clozapine.

## Test yourself

Think of the answer, then tap the question to see it.

## Which receptor actions explain olanzapine's weight gain?

Blockade of histamine H1 and serotonin 5-HT2C receptors, which increases appetite.

## Which combination is avoided with intramuscular olanzapine?

A parenteral benzodiazepine, because of excessive sedation and cardiorespiratory depression.

## Which tests are checked before and during olanzapine treatment because of metabolic risk?

Weight and waist, fasting glucose or HbA1c, and lipids.

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## Related drugs

- [Clozapine](https://durgical.com/en/pharmacology/clozapine/)
- [Quetiapine](https://durgical.com/en/pharmacology/quetiapine/)
- [Risperidone](https://durgical.com/en/pharmacology/risperidone/)

[← Back to the class: Second-generation antipsychotics](https://durgical.com/en/pharmacology/classes/second-generation-antipsychotics/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - OLANZAPINE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2ae07ad4-4e58-4740-9f02-035ec061fefc) (DailyMed (U.S. National Library of Medicine), 2026); [Olanzapine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a601213.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/?query=olanzapine) (World Health Organization, 2025); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 19 (McGraw Hill, 2023).

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Representative model, for educational purposes only.

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