Clozapine for schizophrenia


Generic Name Brand Name
clozapine Clozaril

The U.S. Food and Drug Administration (FDA) approved clozapine for treating suicidal behavior associated with schizophrenia or for treating severe schizophrenia that has not improved with other medicines. Its use for treating other symptoms of schizophrenia has not yet been approved in the U.S., except through special authorization.

When you use this medicine, your name goes into the Clozaril National Registry so that if you have severe side effects, you are not given the medicine again.

How It Works

Clozapine is a newer 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.

  • The U.S. Food and Drug Administration (FDA) 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.2 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 older antipsychotic medicines, people with 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. Koller E, et al. (2001). Clozapine-associated diabetes. American Journal of Medicine, 111(9): 716–723.
  2. Goff DC, et al. (2001). Schizophrenia. Medical Clinics of North America, 85(3): 663–689.

Last Updated: August 28, 2008

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