Olanzapine — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Olanzapine?
Olanzapine is a second-generation (atypical) antipsychotic used for schizophrenia and bipolar disorder. This medication is funded by Pharmac under Special Authority for schizophrenia and bipolar disorder.
What is Olanzapine Used For?
Used for schizophrenia (acute and maintenance), manic episodes in bipolar disorder, and augmentation in treatment-resistant depression. At low doses, also used for chemotherapy-related nausea.
How Does Olanzapine Work?
Blocks dopamine D1/D2/D4, serotonin 5-HT2A, histamine H1, and muscarinic receptors. Dopamine and serotonin antagonism accounts for antipsychotic effects; histamine blockade causes sedation and weight gain.
How to Take Olanzapine
Usually once daily at bedtime. Doses range from 5–20 mg/day. Tablets, orodispersible wafers (Zyprexa Zydis®), and depot injection (Zypadhera®) are available.
Common Side Effects of Olanzapine
- Weight gain (significant — more than most antipsychotics)
- Sedation
- Dry mouth
- Constipation
- Elevated blood glucose
- Elevated triglycerides and cholesterol (metabolic syndrome)
- Dizziness on standing
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Type 2 diabetes and metabolic syndrome (regular monitoring essential)
- Tardive dyskinesia
- Neuroleptic malignant syndrome (rare)
- QT prolongation
- Agranulocytosis (rare)
Drug Interactions
Olanzapine may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Fluvoxamine (significantly increases olanzapine levels)
- Carbamazepine (reduces levels)
- CNS depressants
- Antidiabetic medicines (dose adjustment may be needed)
- IV benzodiazepines with IM olanzapine (severe cardiorespiratory risk — do not combine)
New Zealand Prescribing Information
Olanzapine (2.5–10 mg tablets — Zyprexa® and generics; Zyprexa Zydis® wafers) is funded under Special Authority. Metabolic monitoring mandatory at baseline and every 3–6 months: weight, glucose, HbA1c, and fasting lipids.
Frequently Asked Questions
Why does olanzapine cause weight gain?
Histamine H1 receptor blockade stimulates appetite and reduces satiety. Metabolic changes also promote fat storage and raise blood glucose and triglycerides. Regular monitoring and lifestyle support are essential.
Can I take olanzapine if I have diabetes?
Olanzapine worsens blood glucose control. Diabetes medicines may need adjustment — inform your GP and diabetes team when starting olanzapine.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: