Clozaril treats schizophrenia. Your doctor will need to monitor your blood counts while you are taking this medication.

Clozaril Overview


Clozaril is a prescription medication used to treat the symptoms of schizophrenia (a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or inappropriate emotions) in patients who have not been helped by other medications or who have tried to kill themselves and are likely to try to kill or harm themselves again.

Clozaril is in a class of medications called atypical antipsychotics. It works by changing the activity of certain natural substances in the brain.This medication comes in tablet form and is taken usually one to three times a day.

Common side effects of Clozaril include sedation, tachycardia (fast heartbeat), and constipation.

Clozaril can also cause drowsiness and dizziness. Do not drive or operate heavy machinery until you know how Clozaril affects you.

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  • Other
  • Bipolar Disorder
  • Psychotic Disorders
  • Schizophrenia
  • Schizophrenia And Disorders With Psychotic Features

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  • A month or so
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Uses of Clozaril

Clozaril is a prescription medication used to treat the symptoms of schizophrenia (a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or inappropriate emotions) in patients who have not been helped by other medications or who have tried to kill themselves and are likely to try to kill or harm themselves again.

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.



For more information on this medication choose from the list of selections below.

Clozaril Drug Class

Clozaril is part of the drug class:

Side Effects of Clozaril

Serious side effects have been reported with Clozaril. See the “Clozaril Precautions” section.

Common side effects of Clozaril include the following:

  • sedation
  • dizziness/vertigo
  • headache
  • tremor
  • tachycardia (fast heartbeat)
  • low blood pressure
  • syncope  (fainting or “passing out”)
  • hypersalivation
  • sweating
  • dry mouth
  • visual disturbances
  • constipation
  • nausea
  • fever

Tell your doctor if you have any side effect that bothers you or that does not go away.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Clozaril Interactions

Tell your doctor about all the medicines you are taking or are planning to take including prescription and non-prescription medicines, vitamins, and herbal supplements. Clozaril and other medicines may affect each other. Always check with your doctor before starting or stopping any medicines. Especially tell your doctor if you take:

  • Methotrexate (Rheumatrex, Trexall)
  • Medications used to treat Crohn's disease, psoriasis, and certain cancers
  • Valganciclovir hydrochloride (Valcyte)
  • Drugs to lower blood pressure such as:
    • angiotensin-converting enzyme (ACE) blockers such as benazepril (Lotensin, Lotensin HCT), captopril (Capoten, Capozide), enalapril (Vasotec, Vaseretic), fosinopril (Monopril, Monopril HCT), lisinopril (Prinivil, Prinzide, Zestril, Zestoretic), moexipril (Univasc, Uniretic), quinapril (Accupril, Accuretic, Quinaretic), ramipril (Altace), trandolapril (Mavik, Tarka)
    • angiotensin receptor II blockers such as azilsartan (Edarbi), candesartan (Atacand), irbesartan (Avapro), losartan (Cozaar), olmesartan (Benicar), telmisartan (Micardis, Twynsta), valsartan (Diovan)
    • diuretics such as acetazolamide (Diamox), amiloride (Midamor), bumetanide (Bumex), chlorothiazide (Diuril), chlorthalidone (Thalitone), furosemide (Lasix), hydrochlorothiazide (Microzide, HCTZ), metolazone (Zaroxolyn), torsemide (Demadex), triamterene (Dyrenium, Dyazide, Maxzide)
    • beta blockers such as metoprolol (Toprol XL, Lopressor), carvedilol (Coreg), bisoprolol (Zebeta), betaxolol (Kerlone), nebivolol (Bystolic), propranolol (Inderal)
    • calcium channel blockers such as nifedipine (Adalat, Nifedical, Procardia), amlodipine (Norvasc), verapamil (Calan, Isoptin, Covera, Verelan), diltiazem (Cardizem)
    • vasodilators such as doxazosin (Cardura), prazosin (Minipress), terazosin (Hytrin), clonidine (Catapres), hydralazine (Bidil, Hydrazide), ­minoxidil (Loniten)     
  • anticholinergics such as glycopyrrolate (Cuvposa, Robinul), trospium (Sanctura), oxybutynin (Anturol, Gelnique, Oxytrol, Ditropan), solifenacin (Vesicare), dicyclomine (Bentyl), propantheline (Pro­Banthine), atropine (Atropen)
  • phenytoin (Dilantin)                        
  • rifampin 
  • cimetidine (Tagamet)                                                                       
  • caffeine 
  • citalopram (Celexa)
  • ciprofloxacin (Cipro, Cipro XR)
  • erythromycin (Ery-tab, Eryc)
  • antiarrhythmics such as propafenone, flecainide, encainide, quinidine

This is not a complete list of Clozaril drug interactions. Ask your doctor or pharmacist for more information.

Clozaril Precautions

Serious side effects have been reported with Clozaril including the following:

  • Serious blood problems. Clozaril can cause some very serious blood problems that you will not be able to feel. Your doctor will check your blood at regular visits and it is important that you have your blood tests done when they are scheduled. The pharmacy will give you this medicine only if your blood tests show that it is safe for you to take it. The blood test results would help your doctor to make sure the medicine is working properly and change the dosage if needed.
  • Low white blood cell count. Clozaril can temporarily lower your while blood cell count and increase your chance of getting an infection. Possible signs and symptoms include fever, feeling tired, sore throat, or weakness. Precautions you should take when your blood count is low to reduce the risk of getting an infection include:
    • avoiding people with infection if you can
    • being careful when using a regular toothbrush, dental floss, or toothpick. You doctor, dentist, or nurse may recommend other ways to clean your teeth and gums.
    • Do not touch your eyes or inside your nostril unless you have thoroughly wash your hands.

Let your doctor know immediately if you think you have the flu or getting an infection. Possible signs and symptoms include fever or chills, feeling tired, sore throat, cough or hoarseness, lower back or side pain, painful or difficult urination or weakness.

  • Heart problems. Tell your doctor immediately if you experience chest pain or discomfort, a fast heartbeat, trouble breathing, or fever and chills. 
  • QT prolongation (changes in your heart rhythm). Clozaril changes in your heart rhythm. It may cause fainting or serious side effects in some patients. Contact your doctor right away if you have symptoms of heart rhythm problems such as fast, pounding, or uneven heart beats.
  • Increased dizziness, lightheadedness, or fainting. When you begin to take Clozaril or the dose is increased dizziness, lightheadedness, or fainting may occur, especially when you suddenly get up from a lying or sitting position. Getting up slowly may help. If this problem persists or gets worse, check with your doctor.
  • Increase in blood sugar. Consult your doctor right away if you have increased thirst or urination. Patients with diabetes should check their blood sugar levels more often than normal while taking Clozaril.
  • Increase in watering of the mouth or dryness of the mouth. If you get mouth dryness, for temporary relief chew a sugarless gum or suck on a hard candy or melt bits of ice in your mouth or use a saliva substitute (check your pharmacist). If the dryness persists for more than two weeks check your doctor or dentist. Prolonged dry mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.
  • Neuroleptic malignant syndrome (NMS). Tell your doctor immediately if you notice convulsions (seizures), difficulty with breathing, fast heartbeat, high fever, high or low blood pressure, increased sweating, loss of bladder control, severe muscle stiffness, unusually pale skin, or tiredness. 
  • Tardive dyskinesia (an involuntary movement disorder). This may occur among the elderly, especially elderly women. Stop using this medicine and consult your doctor if you have any of the following symptoms while taking Clozaril: lip smacking or puckering, puffing of the cheeks, rapid or worm-like movements of the tongue, uncontrolled chewing movements, or uncontrolled movements of the arms and legs.
  • Liver problems. Tell your doctor immediately if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin.

Do not stop taking it without first checking with your doctor. Your doctor may want to gradually reduce your dose before stopping Clozaril completely. This would prevent the condition from suddenly coming back and decrease the chance of getting symptoms as headaches, vomiting, nausea, and diarrhea.

Clozaril may cause drowsiness, blurred vision or convulsions (seizures). Do not drive, operate machines, or do anything else that could be dangerous until you know how Clozaril affects you.

Do not take Clozaril if you are allergic to clozapine.

Inform MD

Make sure you tell your doctor if you have any other medical problems, especially:

  • If you have ever had any unusual or allergic reaction to Clozapine
  • Alcohol abuse
  • Blood clotting problems (e.g. deep vein thrombosis, pulmonary embolism)
  • Blood vessel problems (poor circulation)
  • Head injury
  • Recent or history of heart attack(s), heart disease and/or heart failure
  • Heart rhythm problems (e.g. arrhythmia, long QT syndrome, slow heart rate)
  • Hypokalemia (low potassium in the blood)
  • Hypomagnesia (low magnesium in the blood)
  • Hypotension (low blood pressure)
  • Lung problems
  • Stroke(s) (may cause side effects to be worse)
  • Blood diseases (e.g. agranulocytosis/granulocytopenia ( a decrease of a type of white blood cells)
  • Bone marrow disorder
  • Intestinal blockage (e.g.  paralytic ileus (intestinal blockage)
  • Bowel problems (e.g. constipation)
  • Diabetes and hyperglycemia (high blood sugar)
  • Difficult urination
  • Dyslipidemia (high fat in the blood)
  • Enlarged prostate
  • Glaucoma (narrow-angle)
  • Liver disease (e.g. hepatitis)
  • Neuroleptic malignant syndrome (see precautions)
  • Seizures (epilepsy) - Use Clozaril with caution as it may make the condition worse. If seizures are poorly controlled clozapine should not be used.
  • Kidney disease or liver disease—Use with caution. The effects of Clozaril may be increased because of slower removal of the medicine from the body.

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Clozaril and Pregnancy

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Clozaril falls into category B. There are no adequate or well-controlled studies of Clozaril in pregnant women. In animal studies, pregnant animals were given this medication, and the babies did not show any medical issues related to this medication.


Clozaril and Lactation

Tell your doctor if you are breastfeeding or plan to breastfeed.

Clozaril has been detected in human milk. Because of the possibility for adverse reactions in nursing infants from Clozaril, a choice should be made whether to stop nursing or to stop use of this medication. Do not breastfeed infants because of the potential for serious adverse reactions from Clozaril.

Clozaril Overdose

If you take too much Clozaril, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

The most commonly reported signs and symptoms associated with Clozaril overdose are:

  • Sedation
  • Delirium
  • Coma
  • Tachycardia (fast heart rate)
  • Hypotension (low blood pressure)
  • Respiratory depression or failure
  • Hypersalivation (increase saliva)

Clozaril FDA Warning

Clozaril can cause a serious blood condition. Your doctor will order certain lab tests before you start your treatment, during your treatment, and for at least 4 weeks after your treatment. Your doctor will order the lab tests once a week at first and may order the tests less often as your treatment continues. If you experience any of the following symptoms, call your doctor immediately: extreme tiredness; weakness; fever, sore throat, chills, or other signs of flu or infection; or sores in your mouth or throat.

A program has been set up to be sure that people do not take Clozaril without the necessary monitoring. You, your doctor, and your pharmacist must be registered with the program, and your pharmacist will not dispense your medication unless he or she has received the results of your blood tests. Ask your doctor for more information about this program and how you will receive your medication.

Clozaril may cause seizures. Tell your doctor if you have or have ever had seizures. Do not drive a car, operate machinery, swim, or climb while taking Clozaril, because if you suddenly lose consciousness, you could harm yourself or others.

Clozaril may cause myocarditis (swelling of the heart muscle that may be dangerous). If you experience any of the following symptoms, call your doctor immediately: extreme tiredness; difficulty breathing or fast breathing; fever; chest pain; or fast, irregular, or pounding heartbeat.

Clozaril may cause dizziness, lightheadedness, or fainting when you stand up, especially when you first start taking it or when your dose is increased. Tell your doctor if you are taking medications for anxiety such as diazepam (Valium), sleeping pills, or other medications for schizophrenia. Your doctor will probably start you on a low dose of clozapine and gradually increase your dose to give your body time to adjust to the medication and decrease the chance that you will experience this side effect. Talk to your doctor if you do not take Clozaril for 2 days or longer. Your doctor will probably tell you to restart your treatment with a low dose of Clozaril.

Use in Older Adults:

Studies have shown that older adults with dementia (a brain disorder that affects the ability to remember, think clearly, communicate, and perform daily activities and that may cause changes in mood and personality) who take antipsychotics (medications for mental illness) such as Clozaril have an increased chance of death during treatment.

Clozaril is not approved by the Food and Drug Administration (FDA) for the treatment of behavior problems in older adults with dementia. Talk to the doctor who prescribed clozapine if you, a family member, or someone you care for has dementia and is taking this medication.