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Generic Name: Clozapine (KLOE-za-peen)

Drug Class: Antipsychotics

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Clozaril (clozapine) is a medicine that is used to treat schizophrenia and schizoaffective disorders by decreasing hallucinations as well as reduce the risk of suicidal behavior. It is classified as an antipsychotic.

This medicine is usually prescribed when other antipsychotic medicines have not helped.  It is thought that this class of drugs works by decreasing abnormal excitement and activity in the brain’s neuron network.

This information is for educational purposes only. Not every known side effect, adverse effect, or drug interaction is in this database. If you have questions about your medicines, talk to your health care provider.

U.S. Food and Drug Administration Alert:

While clozapine is beneficial for some, there are risks associated with this drug. Specifically, clozapine can decrease the number of neutrophils in the blood. Neutrophils are a type of white blood cell that assists in fighting off infections in the body. In some instances when neutrophils are significantly decreased, severe neutropenia can result leaving a patient prone to infections — particularly those caused by bacteria. Due to this risk, patients taking clozapine need to have their absolute neutrophil count (ANC) monitored on a regular basis. It is this monitoring requirement which serves as the basis for the Clozapine risk evaluation and mitigation strategy (REMS). For more information, please visit the FDA Clozapine information page.

How to Take It

Clozapine should be taken exactly as directed. It comes in tablet form and is taken orally one to three times a day. Your dose of clozapine may need to be adjusted, especially in the first few weeks. You will need to take weekly blood tests while taking clozapine and continue until 4 weeks after you stop taking clozapine. Initially, you will only receive a weeks’ supply at a time. Continue to take this medicine even if you are feeling better. This medicine must be taken for a few weeks for you to feel its full effects.

Side Effects

Side effects that may occur while taking this medicine include:

  • drooling
  • dry mouth
  • constipation
  • fever
  • weight gain
  • vision issues
  • lightheadedness
  • dizziness
  • nausea / vomiting
  • restlessness

Contact your doctor immediately if you experience:

  • tremor
  • seizures
  • difficulty urinating
  • confusion
  • eye pain
  • sweating
  • fever
  • hyperventilation
  • indigestion
  • chest pain
  • pounding in the ears
  • irregular or fast heartbeat

Warnings & Precautions

  • Clozapine may cause low blood pressure or dizziness when you stand up too quickly. This may happen when you first start taking the medicine.
  • Clozapine can cause a serious blood condition that you need to be aware of. Your doctor may order lab treatments before, during, and after taking this medication.
  • Tell your doctor if you have or have had a heart attack, heart failure, or a slow, irregular heartbeat or are taking medications for high blood pressure.
  • This medication may cause seizures. Tell your doctor if you have or have every had a seizure. Do not perform hazardous tasks including driving while taking this medication.
  • This medication may cause swelling of the heart muscle. Call your doctor immediately if you experience any of the following symptoms:  fever, extreme tiredness, difficulty breathing, chest pain, or fast / irregular heartbeat.
  • Tell your doctor if you are allergic to clozapine or any other medications for schizophrenia.
  • For an overdose, seek medical attention immediately. For non-emergencies, contact your local or regional poison control center at 1-800-222-1222.

Drug Interactions

Before taking any new medicine, either prescription or over-the-counter, check with your doctor or pharmacist. This includes supplements and herbal products.

Dosage & Missed Dose

Clozapine is usually taken 1-3 times/day. It is available as either an orally disintegrating tablet or a tablet taken by mouth.

It is best to take this drug around the same time each day.

Follow the directions on the prescription label carefully and take the dosage prescribed.

Take your next dose as soon as you remember. If it is time for your next dose, skip the missed dose and go back to your regular schedule. Do not double doses or take extra medicine to make up for the missed dose. If you miss two days of dosages, call your doctor before taking it again.


Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (preferably not in the bathroom). Throw away any medication that is outdated or no longer needed.


If you plan on becoming pregnant, discuss with your doctor the benefits and risks of using this medicine during pregnancy. It is NOT known if this medicine is excreted in breast milk. It is recommended that you DO NOT breast-feed while taking this medicine unless your doctor or pediatrician has told you to.

More Information

For more information, talk to your doctor, pharmacist, or health care provider, or you can visit this website, for additional information from the manufacturer of this drug.



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APA Reference
Psych Central. (2018). Clozaril. Psych Central. Retrieved on October 26, 2020, from


Scientifically Reviewed
Last updated: 8 Oct 2018
Last reviewed: By Christine Traxler, M.D.
Published on All rights reserved.