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A plain-language summary of the cited sources below. Informational only — not medical advice.
Olanzapine is an atypical antipsychotic medication that works across several receptor systems in the brain. It was developed as an alternative to an older medication called clozapine, specifically designed so that people taking it wouldn't need regular blood tests to monitor their blood cell counts. Doctors prescribe olanzapine to treat schizophrenia and related psychoses, and for managing episodes in bipolar I disorder—either acute manic episodes (sometimes combined with lithium or valproate) or to prevent manic, mixed, or depressive episodes from returning.
After someone takes olanzapine, it stays active in the body for an average of 33 hours in adults, though this can range from 21 to 54 hours depending on the person. In elderly people, the medication clears more slowly, with an average half-life of about 52 hours. The liver processes olanzapine using two main enzyme pathways, CYP1A2 and CYP2D6, breaking it down into metabolites that are much less active than the original medication.
Weight gain is a common effect of olanzapine that families should watch for. Other common effects include drowsiness, feeling lightheaded when standing up quickly (orthostatic hypotension), constipation, and dry mouth. These effects don't happen to everyone, but they occur frequently enough that it's worth being aware of them.
Serious adverse effects are less common but important to know about. These include neuroleptic malignant syndrome (a rare but severe reaction to antipsychotic medications), diabetic coma, and diabetic ketoacidosis. Olanzapine can also increase the risk of blood clots in veins, including pulmonary embolism and deep vein thrombosis. Heart-related serious effects include QT prolongation (a change in heart rhythm that shows up on an ECG), ventricular arrhythmia, torsades de pointes (a specific type of abnormal heart rhythm), cardiac arrest, and sudden unexplained death. If your family member experiences symptoms like high fever with muscle stiffness, severe confusion, chest pain, sudden shortness of breath, or leg pain and swelling, seek medical attention immediately.
Olanzapine should not be used in people who have had an allergic reaction to any ingredient in the product.
Common off-label uses observed in AU practice — none of these are TGA-approved indications for this substance. If the documented purpose is one of these, the prescription falls outside the TGA-approved set and may sit inside the chemical-restraint frame depending on jurisdiction and context.
These are practitioner observations, not TGA-approved indications. A use being off-label does not by itself imply a regulated restrictive practice; review the documented purpose against the observed function in context.
Tier 4 · ObservationBipolar I disorder Clinical criteria: The treatment must be maintenance therapy.
“Olanzapine is an atypical antipsychotic, antimanic and mood stabilising agent that demonstrates a broad pharmacological profile across a number of receptor systems.”
“After oral administration to healthy subjects, the mean terminal elimination half-life was 33 hours (21 to 54 hours for 5th to 95th percentile) and the mean olanzapine plasma clearance was 26 L/hr (12 to 47 L/hr for the 5th to 95th percentile).”
A plain-language summary of the cited sources below. Informational only — not medical advice.
Olanzapine is a thienobenzodiazepine atypical antipsychotic developed as a structural analogue of clozapine, with a broad receptor profile across dopaminergic, serotonergic, adrenergic, histaminergic and muscarinic systems. It carries TGA approval for the treatment of schizophrenia and related psychoses, the acute treatment of manic episodes in bipolar I disorder (alone or in combination with lithium or valproate), and prevention of recurrence in bipolar I disorder. The only listed contraindication is known hypersensitivity to any ingredient of the product.
Following oral administration, mean terminal elimination half-life is approximately 33 hours in adults (21–54 hours across the 5th to 95th percentile) and extends to 51.8 hours in elderly patients; mean plasma clearance is 26 L/hr (range 12–47 L/hr). Metabolism occurs primarily via CYP1A2 and CYP2D6, yielding N-desmethyl and 2-hydroxymethyl metabolites that exhibit significantly less pharmacological activity than the parent compound. Common adverse effects include weight gain, somnolence, orthostatic hypotension, constipation and dry mouth. Serious adverse effects encompass neuroleptic malignant syndrome, diabetic ketoacidosis and diabetic coma, venous thromboembolism (including pulmonary embolism and deep vein thrombosis), and cardiac events including QT prolongation, ventricular arrhythmia, torsades de pointes, cardiac arrest and sudden unexplained death.
Working under the parallel aged-care framework? Aged-care equivalent →
Curated subset. The full adverse-effect list is in the TGA Product Information; click any citation above to open it.
“Cytochromes P450-CYP1A2 and P450-CYP2D6 contribute to the formation of the N-desmethyl and 2-hydroxy-methyl metabolites, both exhibited significantly less in vivo pharmacological activity than olanzapine in animal studies.”