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Olanzapine: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Aug 17, 2022.

1. How it works

  • Olanzapine may be used to treat schizophrenia or bipolar disorder.
  • Experts aren't exactly sure how olanzapine works but suggest it has effects on neurotransmitters such as dopamine and serotonin in the brain.
  • Olanzapine belongs to the class of medicines known as atypical antipsychotics. Atypical means it is less likely than older antipsychotics to cause movement-related side effects.

2. Upsides

  • May be used to relieve symptoms associated with schizophrenia in adults and children aged 13 years and older.
  • May be used for the treatment of manic or mixed episodes of bipolar I disorder in adults and children aged 13 years and older.
  • May also be used in addition to fluoxetine for the treatment of treatment-resistant depression and depression associated with bipolar I disorder in adults and children older than ten years.
  • Relieves symptoms such as hallucinations (hearing or seeing things that are not actually there), disturbing thoughts (such as paranoia or suspicion), lack of emotion, anxiety, aggression, or agitation.
  • Less likely than haloperidol or risperidone to cause movement-related side effects.
  • Unlike clozapine, is not associated with a risk of agranulocytosis (a severe type of white blood cell disorder).
  • Unlikely to cause clinically significant hyperprolactinemia or prolongation of the QT interval.
  • Generic olanzapine is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Dizziness, a drop in blood pressure on standing, inner restlessness, constipation, and non-aggressive objectionable behavior. Weight gain of approximately 2.6kg (5.7 pounds) over six weeks is also common.
  • Other reasonably common side effects include dry mouth, lazy eye, and extrapyramidal symptoms (such as restlessness, tremor, uncontrolled muscle contractions). May also cause difficulty swallowing.
  • May increase blood sugar levels. People with a history of diabetes or at risk of diabetes should be monitored closely. May also cause undesirable changes in blood lipids (cholesterol and triglycerides) especially in teenagers aged 13 to 17 or when used in combination with fluoxetine in children aged 10 to 17.
  • May cause drowsiness and affect a person's ability to drive or operate machinery. Avoid alcohol.
  • Should not be used for the treatment of dementia-related psychosis in elderly people as associated with a higher risk of death.
  • Potentially irreversible tardive dyskinesia can develop, even with low dosages used short-term. Symptoms include facial grimacing, repetitive chewing, and tongue thrusting.
  • Rarely, may cause Neuroleptic Malignant Syndrome; symptoms include high body temperature, muscle rigidity, and mental disturbances; discontinue immediately and seek urgent medical advice.
  • Blood counts may need monitoring as olanzapine can cause numbers of white blood cells to decrease.
  • May affect body temperature regulation and reproductive and sexual function. May not be suitable for some people such as those with glaucoma, cardiovascular disease, prostate enlargement, liver disease, a history of seizures, or in the elderly.
  • May interact with several drugs, including anti-hypertensive agents, antidepressants, and levodopa. See prescribing information for a full list of interactions.
  • Should only be given during pregnancy if potential benefits outweigh risks. Reports of agitation, hypotonia, tremor, sleepiness, respiratory distress, and feeding disorders have been reported in neonates exposed to antipsychotics during the third trimester of pregnancy. Animal studies have shown adverse effects on the fetus but there are no controlled studies in humans. Olanzapine is not recommended during breastfeeding.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

  • Olanzapine is an oral antipsychotic that may be used to treat schizophrenia or bipolar disorder. Weight gain is common in people who take olanzapine.

5. Tips

  • Report any symptoms of increased thirst, increased urination, increased appetite, or weakness to your doctor.
  • May be administered with or without food.
  • Read the medication guide that comes with olanzapine tablets before you start taking them.
  • Olanzapine is available as orally-disintegrating tablets (Zyprexa Zydis). Open by peeling back the foil on the blister with dry hands (do not push the tablet through the foil). Remove and place the entire Zyprexa Zydis tablet on the tongue; disintegration should occur rapidly.
  • May cause sedation or impair judgment skills and affect your ability to drive or operate machinery.
  • Do not drink alcohol while you are taking olanzapine.
  • Avoid overheating and dehydration.
  • Make sure you eat a healthy, balanced diet and exercise regularly. Weight gain is common with olanzapine and your doctor may regularly weigh you to ensure that you are not putting on too much weight. Your doctor may also do regular cholesterol and triglyceride tests because olanzapine may also cause high lipid levels in your blood.
  • People with diabetes may need to check their blood sugar levels more regularly while taking olanzapine. Call your doctor if you have any symptoms of high blood sugar, such as feeling very thirsty, need to urinate more often, feeling very tired, nauseous, or confused.
  • Talk to your doctor if you are feeling depressed or are having thoughts of suicide.
  • Seek urgent medical advice if you develop uncontrolled body movements, confusion, high fever, lightheadedness, fainting, seizures, have problems controlling your body temperature, or difficulty swallowing.
  • Talk to your doctor if you are intending to become pregnant or are already pregnant before you take olanzapine. If you inadvertently become pregnant, ask your doctor about enrolling on the pregnancy registry for atypical antipsychotics.

6. Response and effectiveness

  • Peak blood levels are reached within six hours of taking a single dose of oral olanzapine. Effects are long-lasting, so olanzapine should be dosed once a day; however, it may take several weeks of continued dosing before a reduction in symptoms is seen.
  • Concentrations of olanzapine in the blood reach a steady level after approximately one week of regular dosing.

7. Interactions

Medicines that interact with olanzapine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with olanzapine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with olanzapine include:

  • amisulpride
  • anticholinergic agents, such as benztropine or oxybutynin
  • antidepressants such as citalopram, escitalopram, or fluoxetine
  • antipsychotics such as aripiprazole, clozapine, or haloperidol
  • azelastine
  • bupropion
  • cannabidiol
  • cannabis
  • carbamazepine
  • clozapine
  • cisapride
  • CYP1A2 inducers such as cimetidine, ciprofloxacin, enoxacin, and fluvoxamine
  • CYP1A2 inhibitors, such as rifampin and barbiturates, and tobacco smoke
  • diuretics, such as furosemide, or hydrochlorothiazide
  • droperidol
  • heart medications, such as amlodipine, betaxolol, candesartan, carisprodol
  • HIV medications, such as indinavir, nelfinavir, ritonavir, and saquinavir
  • insulin
  • ipratropium or tiotropium
  • glucagon
  • kava kava
  • lithium
  • magnesium sulfate
  • medications used to treat Parkinson's Disease, such as cabergoline and levodopa
  • nitroglycerin
  • opioids, such as alfentanil, fentanyl, buprenorphine, methadone, or oxycodone
  • pimozide
  • potassium chloride
  • QT-prolonging medications, such as amiodarone, clarithromycin, domperidone, flupentixol, sotalol, or voriconazole
  • tramadol
  • valproate
  • zolpidem.

Avoid drinking alcohol or taking illegal or recreational drugs while taking olanzapine.

Note that this list is not all-inclusive and includes only common medications that may interact with olanzapine. You should refer to the prescribing information for olanzapine for a complete list of interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use olanzapine only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2023 Revision date: August 17, 2022.