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Clozaril Side Effects Center
Medical Editor: Melissa Conrad Stöppler, MD
Clozaril (clozapine) is an antipsychotic medication that is used to treat severe schizophrenia symptoms in people who have not responded to other medications. Clozapine is also used to help reduce the risk of suicidal behavior in people with schizophrenia or similar disorders. Side effects can include constipation, drooling, sleep disorders, increased sweating, or weight gain. Other side effects can occur. Clozaril is taken orally in tablet form, and an orally-disintegrating tablet that can be taken without water is available.
While you are taking clozapine, your blood may need to be tested every week for the first 6 months of treatment. It has been associated with agranulocytosis in some patients, a potentially fatal decrease in a certain type of white blood cells. Clozaril is not expected to be harmful to an unborn baby. Do not use clozapine without telling your doctor if you are pregnant or plan to become pregnant during treatment. Clozapine can pass into breast milk and may harm a nursing baby.
Our Clozaril Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Clozaril in Detail - Patient Information: Side Effects
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Serious and sometimes fatal infections may occur during treatment with clozapine. Call your doctor right away if you have signs of infection such as:
- fever, chills, body aches, flu symptoms;
- mouth and throat ulcers;
- cough, sore throat;
- rapid heart rate; or
- rapid and shallow breathing.
Stop using clozapine and call your doctor at once if you have any of these serious side effects:
- seizure (black-out or convulsions);
- skin rash, bruising, severe tingling, numbness, pain, muscle weakness;
- fast or pounding heartbeats, chest pain, unusual tiredness, trouble breathing;
- feeling short of breath (even at night or with mild exertion), swelling in your hands or feet;
- feeling like you might pass out;
- slow heart rate, weak pulse, fainting, slow breathing (breathing may stop);
- high blood sugar (increased thirst, extreme hunger, fruity breath odor, increased urination, drowsiness);
- very stiff (rigid) muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors;
- twitching or uncontrollable movements of your eyes, lips, tongue, face, arms, or legs; or
- nausea, vomiting, loss of appetite, and jaundice (yellowing of your skin or eyes).
Less serious side effects may include:
- dry mouth, blurred vision;
- drooling, especially at night;
- increased sweating;
- drowsiness, dizziness, spinning sensation; or
- sleep problems.
Read the entire detailed patient monograph for Clozaril (Clozapine) »
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Clozaril Overview - Patient Information: Side Effects
To prevent constipation, maintain a diet adequate in fiber, drink plenty of water, and exercise. If you become constipated while using this drug, consult your pharmacist for help in selecting a laxative (e.g., stimulant-type with stool softener).
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor immediately if any of these unlikely but serious side effects occur: facial/muscle twitching, signs of infection (e.g., severe tiredness, fever, persistent sore throat), seizures, uncontrollable movements, change in the amount of urine.
Seek immediate medical attention if any of these rare but very serious side effects occur: high fever, fast/irregular heartbeat, severe dizziness, fainting, muscle stiffness, mental/mood changes, difficulty breathing with exercise, swollen legs/feet, sudden weakness, pain/redness/swelling of the arms/legs, chest pain, dark urine, persistent nausea/vomiting, stomach/abdominal pain, yellowing of eyes/skin.
A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Clozaril (Clozapine)»
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Clozaril FDA Prescribing Information: Side Effects
Associated with Discontinuation of Treatment
Sixteen percent of 1,080 patients who received CLOZARIL® (clozapine) in premarketing clinical trials discontinued treatment due to an adverse event, including both those that could be reasonably attributed to CLOZARIL treatment and those that might more appropriately be considered intercurrent illness. The more common events considered to be causes of discontinuation included: CNS, primarily drowsiness/sedation, seizures, dizziness/syncope; cardiovascular, primarily tachycardia, hypotension and ECG changes; gastrointestinal, primarily nausea/vomiting; hematologic, primarily leukopenia/ granulocytopenia/ agranulocytosis; and fever. None of the events enumerated accounts for more than 1.7% of all discontinuations attributed to adverse clinical events.
Class Effect: Symptoms of dystonia, prolonged abnormal contractions of muscle groups, may occur in susceptible individuals during the first few days of treatment. Dystonic symptoms include: spasm of the neck muscles, sometimes progressing to tightness of the throat, swallowing difficulty, difficulty breathing, and/or protrusion of the tongue. While these symptoms can occur at low doses, they occur more frequently and with greater severity with high potency and at higher doses of first generation antipsychotic drugs. An elevated risk of acute dystonia is observed in males and younger age groups. Clozapine, an atypical antipsychotic, is associated with a low incidence of dystonia (see WARNINGS, Tardive Dyskinesia).
Adverse events observed in association with the use of CLOZARIL in clinical trials at an incidence of greater than 5% were: central nervous system complaints, including drowsiness/sedation, dizziness/vertigo, headache and tremor; autonomic nervous system complaints, including salivation, sweating, dry mouth and visual disturbances; cardiovascular findings, including tachycardia, hypotension and syncope; and gastrointestinal complaints, including constipation and nausea; and fever. Complaints of drowsiness/sedation tend to subside with continued therapy or dose reduction. Salivation may be profuse, especially during sleep, but may be diminished with dose reduction.
Incidence in Clinical Trials
The following table enumerates adverse events that occurred at a frequency of 1% or greater among CLOZARIL patients who participated in clinical trials. These rates are not adjusted for duration of exposure.
Treatment-Emergent Adverse Experience Incidence Among Patients
Taking CLOZARIL® (clozapine) in Clinical Trials
(excluding the InterSePT™ Study)
(N = 842)
(Percentage of Patients Reporting)
|Body System Adverse Eventa||Percent|
|Central Nervous System|
|Epileptiform Movements/Myoclonic Jerks||1|
|ECG Change/Cardiac Abnormality||1|
|Liver test Abnormality||1|
|Autonomic Nervous System|
|Pain (Back, Neck, Legs)||1|
|Muscle Pain, Ache||1|
|Dyspnea, Shortness of Breath||1|
|a Tongue Numb/Sore Events reported
by at least 1% of CLOZARIL patients are included.
b Rate based on population of approximately 1,700 exposed during premarket clinical evaluation of CLOZARIL.
The following table enumerates adverse events that occurred at a frequency of 10% for either treatment group in patients who took at least 1 dose of study medication during their participation in InterSePT, which was an adequate and well-controlled 2-year study evaluating the efficacy of CLOZARIL relative to Zyprexa in reducing the risk of emergent suicidal behavior in patients with schizophrenia or schizoaffective disorder. These rates are not adjusted for duration of exposure.
Treatment-Emergent Adverse Experience Incidence1
Among Patients Taking CLOZARIL® (clozapine) or Zyprexa® (olanzapine)
in the InterSePT™ Study (Percentage of Patients Reporting)
|Dizziness (excluding vertigo)||27%||12%|
|1AEs are listed by frequency in
CLOZARIL group, and included in the table are those for which the risk
ratio of CLOZARIL over Zyprexa or of Zyprexa over CLOZARIL was greater
NEC - not elsewhere classified
NOS - not otherwise specified
Other Events Observed During the Premarketing Evaluation of CLOZARIL® (clozapine)
This section reports additional, less frequent adverse events which occurred among the patients taking CLOZARIL in clinical trials. Various adverse events were reported as part of the total experience in these clinical studies; a causal relationship to CLOZARIL treatment cannot be determined in the absence of appropriate controls in some of the studies. The table above enumerates adverse events that occurred at a frequency of at least 1% of patients treated with CLOZARIL. The list below includes all additional adverse experiences reported as being temporally associated with the use of the drug which occurred at a frequency less than 1%, enumerated by organ system.
Central Nervous System: loss of speech, amentia, tics, poor coordination, delusions/hallucinations, involuntary movement, stuttering, dysarthria, amnesia/memory loss, histrionic movements, libido increase or decrease, paranoia, shakiness, Parkinsonism, and irritability.
Urogenital System: dysmenorrhea, impotence, breast pain/discomfort, and vaginal itch/infection.
Postmarketing Clinical Experience
Postmarketing experience has shown an adverse experience profile similar to that presented above. Voluntary reports of adverse events temporally associated with CLOZARIL not mentioned above that have been received since market introduction and that may have no causal relationship with the drug include the following:
Hepatic System: cholestasis.
Urogenital System: acute interstitial nephritis and priapism.
Musculoskeletal System: myasthenic syndrome and rhabdomyolysis.
Vision Disorders: narrow angle glaucoma.
Drug Abuse And Dependence
Physical and psychological dependence have not been reported or observed in patients taking CLOZARIL® (clozapine).
Read the entire FDA prescribing information for Clozaril (Clozapine) »
Additional Clozaril Information
Clozaril - User Reviews
Clozaril User Reviews
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Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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