Olanzapine (Olazax, Zalasta, Zyprexa)

Mechanism of action

Antipsychotic (atypical).

Antagonises several receptors including dopamine receptor D1, D2, D3 and D4, serotonin receptor 5HT2A, 5HT2C, 5HT3, 5HT6, alpha-1 adrenergic receptor, histamine receptor H1 and muscarinic receptors.

Block of D2 receptor, specifically in the mesolimbic pathway, and serotonin 5HT2A receptor in prefrontal cortex are mainly responsible for the antipsychotic effects of olanzapine.  

Indications and dose


Onset of action: 15–45 minutes

Half-life of elimination: 21–54 hours (30 hours on average)

Metabolism: Hepatic

Elimination: Mainly through metabolism, only 7 % as an unchanged drug 

Directions for administration

Starting dose may be adjusted within the range 5–20 mg/day after clinical reassessment. 

Lower starting dose (5 mg) is recommended in patients with severe renal/hepatic impairment.

Metabolism of olanzapine may be induced by smoking although it is not recommended to routinely change the dosage for smokers. 

Medicinal forms

Tablets – 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg, 20 mg


Somnolence, dizziness 

Weight gain

Eosinophilia, leukopenia, neutropenia

Elevation of prolactin, cholesterol, glucose, and triglyceride levels

Transient (asymptomatic) elevations of hepatic aminotransferases

Dyskinesia, parkinsonism

Orthostatic hypotension

Anticholinergic effects


  1. Pharm 101: Olanzapine • LITFL • Top 200 Drugs
  2. Olanzapine: Uses, Interactions, Mechanism of Action | DrugBank Online
  3. https://www.medicines.org.uk/emc/search?q=olanzapine