Pharmacology · 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
The figure shows risperidone in the human D2 receptor; olanzapine blocks the same site (no olanzapine-bound D2 structure exists).
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)
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.
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.
Related drugs
← Back to the class: 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 (DailyMed (U.S. National Library of Medicine), 2026); Olanzapine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (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.