Clozapine for Schizophrenia

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Clozapine for Schizophrenia


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Clozapine is approved in Canada for treating schizophrenia that has not responded well to other treatments. But your doctor will need special authorization to prescribe clozapine for schizophrenia symptoms, and special monitoring is needed when clozapine is used.

When you use this medicine, your name goes into a patient specific registry so that if you have severe side effects, you are not given the medicine again.

How It Works

Clozapine is a second-generation antipsychotic. It is thought to affect the way brain chemicals (neurotransmitters) work.

Why It Is Used

Clozapine is used to treat the symptoms of schizophrenia if other medicines don't work or if the person may be thinking about suicide.

How Well It Works

Clozapine may reduce symptoms of schizophrenia that have not been controlled by other medicines.

Side Effects

Some warnings about serious side effects of clozapine have been issued.

  • Health Canada's Therapeutic Products Directorate (TPD) and the drug maker have strengthened warnings to say that clozapine may cause a possible life-threatening heart problem (myocarditis).
  • Clozapine may make you more likely to develop insulin resistance, diabetes, and hyperglycemia (high blood sugar).1

A rare but possibly life-threatening side effect is agranulocytosis, a problem that causes your body to make fewer white blood cells. You need weekly blood cell tests during the first 6 months of treatment with this medicine and tests every 2 weeks after this period of time.1 This helps the doctor find this side effect early.

The most common side effects of clozapine are:

  • Feeling sleepy or slow (sluggish).
  • Gaining weight.
  • Having more saliva.

Other side effects include:

  • A faster heartbeat.
  • Lower blood pressure.
  • Fever.
  • Seizures, but usually in those taking high doses.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Because of the side effects, talk with your doctor about whether this medicine is right for you. If you have had a seizure, heart or blood vessel problems, or liver or kidney problems, you probably should not take clozapine.

It is not known whether clozapine is safe for children, older adults, and nursing women.

Because clozapine does not have some of the bothersome side effects of the first-generation antipsychotic medicines, people who have schizophrenia may be more likely to take it regularly.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. Durham J (2009). Schizophrenia: A review of pharmacologic and nonpharmacologic treatments. US Pharmacist, 34(11): 1–5.


By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Miklos Ferenc Losonczy, MD, PhD - Psychiatry
Last Revised January 14, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.