David Snyder, PharmD, BCPP, is a board-certified clinical pharmacist and psychopharmacology expert at McLean Hospital in Belmont, Massachusetts.
The Food and Drug Administration (FDA) has issued a boxed warning for Clozaril. Boxed warnings are the agency’s strongest warnings for serious and potentially life-threatening risks. Review these warnings and discuss your concerns with your healthcare provider before starting treatment. The boxed warning indicates:
Clozaril (clozapine ) is a psychiatric medication categorized as a second-generation, or atypical, antipsychotic used for treatment-resistant schizophrenia and suicidal behavior Clozaril works by altering the balance of certain neurotransmitters in the brain.
Clozaril is only available from a certified pharmacy under a special program called the Clozapine Risk Evaluation and Mitigation Strategy (REMS) program.
Clozaril, an orally administered drug, can be taken as a tablet, an orally disintegrating tablet (a tablet that dissolves quickly in the mouth), or as an oral suspension (a liquid).
Brand Name(s): Clozaril, Versacloz
Dosage: Tablet, orally disintegrating tablet, liquid suspension
The FDA approved Clozaril to treat people with severe schizophrenia (a mental health illness that causes disturbed thinking, loss of interest in life, and disturbing emotions) who fail to respond adequately to standard antipsychotic treatment in addition to treating various mental disorders, mood disorders, and schizoaffective disorder.
Additionally, Clozapine alleviates hallucinations and helps prevent suicidal thoughts. The medication helps people think more clearly and positively, experience less anxiety, and actively participate in everyday life.
Take Clozaril as prescribed by your healthcare provider and follow the directions carefully on your prescription label. Ask the pharmacist about anything you do not understand. Use the dosing syringe or a medicine dose-measuring device provided with the medicine.
Do not use a household spoon to measure the dose. Follow the directions provided to use the syringe or ask your pharmacist how to use it properly.
Clozapine comes as a tablet, a disintegrating tablet, and as a liquid suspension, all to be taken orally. It is generally prescribed once or twice a day with or without food. Try to take Clozaril at around the same time(s) every day. Take exactly as directed by a healthcare provider.
When using a disintegrating tablet, use dry hands to open the foil. Immediately place the tablet on your tongue after taking it out of the foil.
The tablet will dissolve and can be swallowed with saliva without water. Do not chew the dissolving tablet and only swallow once after dissolving. If taking an oral suspension, shake it well for 10 seconds before taking a dose.
Store the medicine in the container it comes in, away from heat, light, and moisture. Do not store the medications in the bathroom, as the moisture and heat can affect the quality of Clozaril. Storage temperature should not exceed 86 degrees F.
Do not refrigerate or freeze the oral suspension. Keep all medicines locked away from the sight and reach of children, preferably in a lockbox.
Do not keep expired medicines. Do not throw the unwanted medication in the waste bin, pour it down a drain, or flush it down the toilet.
The best way to discard unwanted medication is through a medicine take-back program. Ask your pharmacist or contact the local waste disposal company.
Notable off-label uses for Clozaril include:
Moreover, Clozaril may offer clinical benefits for people with:
It may take several weeks to notice the benefits of Clozapine when treating the symptoms of schizophrenia. It may take six to 12 months to see the full effects of Clozaril.
Some people may even begin to feel improvement within the first week of starting the medicine.
Clozapine may not work for everyone. If your symptoms do not start to improve within a couple of months, or if the side effects are severe, consult your healthcare provider to discuss other treatment options for you.
This is not a complete list of side effects, and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at fda.gov/medwatch or 800-FDA-1088.
As with all medications, Clozaril can cause side effects. Tell your healthcare provider about any side effects you experience while taking this medication.
The most common side effects of Clozaril are:
The FDA has issued a boxed warning for Clozaril. Boxed warnings are the agency’s strongest warnings for serious and potentially life-threatening risks. Review these warnings and discuss your concerns with your healthcare provider before starting treatment. The boxed warning indicates:
Call your healthcare provider right away if you experience serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.
Serious side effects and symptoms which may occur as a result of Clozaril use include:
Tardive dyskinesia (TD), an involuntary neurological disorder, is a side effect caused by prolonged use of antipsychotics. If you feel symptoms of TD, such as grimacing, sucking, smacking of lips, or other involuntary movements, contact your healthcare provider.
All people taking antipsychotics should regularly complete an Abnormal Involuntary Movement Scale (AIMS) by their healthcare provider to monitor TD. Clozapine has relatively a lower risk of TD compared to older antipsychotics.
Clozaril may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.
If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
Due to the possible adverse effects of this medication, there may be changes to how Clozaril is used. Users should be aware of the following before taking Clozaril:
Severe allergic reaction: Avoid using Clozaril if you have a known allergy to it or any of its ingredients. Ask your pharmacist or healthcare provider for a complete list of the ingredients if you're unsure.
Pregnancy: If you are pregnant, become pregnant, or plan to become pregnant, talk to your healthcare provider to manage your medications. Pregnancy with Clozaril is a complex decision since untreated schizophrenia has risks to the fetus and the mother. It is essential to discuss the risks and benefits of treatment.
Antipsychotic use during the third trimester of pregnancy can cause abnormal muscle movements or withdrawal symptoms in newborns following delivery.
Breastfeeding: Caution is recommended with breastfeeding since Clozaril passes into breast milk. Talk with your healthcare provider if you plan to breastfeed, weigh the benefits and risks of taking Clozaril while nursing, and the different ways available to feed your baby.
Adults over 65: Clozaril should be prescribed according to individual needs. Caution is advised in older people due to decreased kidney function, heart conditions, and other problems. They may need a lower dose of Clozaril.
If you miss a dose of Clozaril, take it as soon as you remember. If it is nearly the time of your next dose, skip the missed dose and take the next dose at the regular time. Do not double the dose or take more than prescribed to make up for the missed dose.
If you miss Clozaril for more than two consecutive days, contact your healthcare provider. You may need a dose adjustment to restart the medicine again.
In case of an accidental overdose of Clozaril, call the Poison Control Center. If the victim has collapsed, has seizures, has trouble breathing, or feels like passing out, immediately call emergency services at 911.
Symptoms of a potential overdose may include:
If you think you or someone else may have overdosed on Clozaril, call a healthcare provider or the Poison Control Center (800-222-1222).
If someone collapses or isn't breathing after taking Clozaril, call 911 immediately.
Clozapine 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. Your doctor will make sure the medicine is working properly and change the dosage if needed.
Clozapine can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. If you can, avoid people with infections. Check with your doctor right away if you think you are getting an infection, or if you have a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
Contact your doctor as soon as possible if you have chest pain or discomfort, a fast or slow heartbeat, trouble breathing, or fever and chills. These can be symptoms of a very serious problem with your heart.
Clozapine may cause drowsiness, blurred vision, convulsions (seizures), or to have trouble with thinking or controlling body movements, which may lead to falls, fractures or other injuries. Do not drive, operate machines, swimming, climbing, or do anything else that could be dangerous until you know how this medicine affects you.
This medicine can cause changes in your heart rhythm, such as a condition called QT prolongation. It may cause fainting or serious side effects in some patients. Contact your doctor right away if you have any symptoms of heart rhythm problems, such as fast, pounding, or uneven heartbeats.
Dizziness, lightheadedness, or fainting may occur, especially when you get up from a lying or sitting position suddenly. These symptoms are more likely to occur when you begin taking this medicine, or when the dose is increased. Getting up slowly may help. If this problem continues or gets worse, check with your doctor.
Clozapine may cause stomach or bowel problems (eg, gastrointestinal hypomotility). Tell your doctor right away if you have severe constipation, nausea, vomiting, or stomach pain or swelling.
This medicine may increase your risk for anticholinergic effects, especially when used with other medicines (eg, benztropine, cyclobenzaprine, or diphenhydramine). Check with doctor right away if you have blurred vision, dizziness, drowsiness, confusion, delirium, or hallucinations, nausea, vomiting, constipation, difficult urination, eye pain, dry eyes, mouth, nose, or throat, flushing or redness of the face, troubled breathing, or fast heartbeat.
For diabetic patients: This medicine may increase the amount of sugar in your blood. Check with your doctor right away if you have increased thirst or urination. Diabetic patients should check their blood and urine sugar levels more often than normal while taking this medicine.
In some patients, clozapine may cause increased watering of the mouth. Other patients, however, may get dryness of the mouth. For temporary relief of mouth dryness, use sugarless gum or candy, melt bits of ice in your mouth, or use a saliva substitute. However, if your mouth continues to feel dry for more than 2 weeks, check with your medical doctor or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.
Check with your doctor right away if you are having 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. These could be symptoms of a serious condition called neuroleptic malignant syndrome (NMS).
This medicine may cause tardive dyskinesia (a movement disorder) among the elderly, especially elderly women. Check with your doctor right away if you have any of the following symptoms while taking this medicine: 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.
Check with your doctor right away 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. These could be symptoms of a serious liver problem.
If you have been using this medicine regularly, do not stop taking it without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are taking before stopping it completely. This is to help prevent the illness from suddenly returning and to decrease the chance of having symptoms such as headache, nausea, vomiting or diarrhea.
This medicine will add to the effects of alcohol and other central nervous system (CNS) depressants, which are medicines that slow down the nervous system and possibly cause drowsiness. Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds, sedatives, tranquilizers, or sleeping medicine, prescription pain medicine or narcotics, medicine for seizures or barbiturates, muscle relaxants, or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using this medicine.
Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before having surgery or medical tests.
Tell your doctor if you smoke or drink products that contain caffeine.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal (eg, St. John's wort) or vitamin supplements.
Clozaril is not appropriate for everyone. You should not take this medication if you are allergic to clozapine or any of the inactive ingredients in Clozaril.
Clozapine is discouraged in people who have conditions such as:
Clozaril should not be used simultaneously with drugs known to cause agranulocytosis or somehow suppress bone marrow function.
Tell your healthcare provider about all of the medicines you take, including prescription and over-the-counter (OTC) medicines, and vitamins or supplements.
Certain medications may affect the levels of Clozaril in the body, which may affect how it works.
Irregular heartbeat (atrial fibrillation) medication, including:
Selective serotonin reuptake inhibitors (SSRIs), including:
Clozaril may interact negatively with oral contraceptives.
Other medicines that treat high blood pressure, anxiety, mental illness, motion sickness, or nausea may also interact negatively with Clozaril. Your healthcare provider may need to alter the dosage of the medicines or monitor you carefully for side effects.
Consult your healthcare provider or pharmacist if you are drinking alcohol or taking drugs that cause drowsiness, including:
Talk to your healthcare provider about any tobacco products you use. Cigarette smoking may reduce the effectiveness of Clozapine.
Second-generation antipsychotics cause fewer movement disorder-related side effects. However, these medicines increase the risk of weight gain and diabetes.
Atypical antipsychotics other than Clozaril approved to treat schizophrenia include:
The lack of statistical and clinical data makes it challenging to analyze the comparative efficacy and effectiveness of newer atypical drugs to judge whether newer drugs are more effective, less effective, or equivalent.
Trials with longer duration, measuring clinically essential outcomes, are needed to assess the actual comparative clinical effectiveness and tolerability of other drugs in relation to Clozapine.
Clozaril is prescribed to treat schizophrenia in people with treatment-resistant schizophrenia. It is also indicated to reduce hallucinations and repetitive suicidal thoughts in people who are likely to harm themselves.
Clozaril and other antipsychotic drugs work by altering the balance of different neurotransmitters in the brain used to treat certain mental disorders.
There are certain drugs that interact with Clozaril to affect its plasma concentration and its bioavailability such as antibiotics such as ciprofloxacin and erythromycin, benztropine, metoclopramide, cimetidine, bupropion, cyclobenzaprine, escitalopram, and others.
The response to Clozaril treatment varies in different people. However, it may take several weeks to notice the benefits of the drug.
A major side effect of Clozaril is a reduction in white blood cells that requires periodic monitoring by your healthcare professional the entire time you are taking it.
This is because the first six months of therapy require weekly monitoring, six to 12 months require monitoring every other week, while greater than 12 months requires monthly ANC monitoring. Seek help immediately if something is unusual or worsening your health.
To stay healthy while using Clozaril, it is vital to closely monitor your overall health. Consult with your healthcare provider about any of the diseases, allergies, and medicines you take. Take Clozaril as directed and follow the procedure before stopping taking this medicine. Immediately report any severe side effects.
Keep all appointments with your healthcare provider and at the lab. Specific lab tests (such as glucose or prolactin levels, lipid levels, or liver tests) are mandatory to determine how you respond to clozapine treatment.
Eat a healthy and well-balanced diet and exercise regularly to avoid gaining weight when taking this medicine.
Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.
Food and Drug Administration. Clozaril (clozapine) prescribing information.
Divac N, Prostran M, Jakovcevski I, Cerovac N. Second-generation antipsychotics and extrapyramidal adverse effects. Biomed Res Int. 2014;2014:656370. doi:10.1155/2014/656370
American Psychiatric Association. The Clozapine Risk Evaluation and Mitigation Strategy (REMS) Program.
Teodorescu A, Dima L, Ifteni P, Rogozea LM. Clozapine for treatment-refractory behavioral disturbance in dementia. Am J Ther. 2018;25(3):e320-e325. doi:10.1097/MJT.0000000000000735
Yatham LN, Kennedy SH, Parikh SV, et al. Canadian Network for Mood and Anxiety Treatments (CANMAT) and International Society for Bipolar Disorders (ISBD) 2018 guidelines for the management of patients with bipolar disorder. Bipolar Disord. 2018;20(2):97-170. doi: 10.1111/bdi.12609
Taddei RN, Cankaya S, Dhaliwal S, Chaudhuri KR. Management of psychosis in Parkinson's disease: emphasizing clinical subtypes and pathophysiological mechanisms of the condition. Parkinsons Dis. 2017;2017:3256542. doi:10.1155/2017/3256542
Kant R, Chalansani R, Chengappa KNR, Dieringer MF. The off-label use of clozapine in adolescents with bipolar disorder, intermittent explosive disorder, or posttraumatic stress disorder. J Child Adolesc Psychopharmacol. 2004;14(1):57-63. doi:10.1089/104454604773840490
National Alliance on Mental Illness. Tardive dyskinesia.
Stacy M, Sajatovic M, Kane JM, et al. Abnormal involuntary movement scale in tardive dyskinesia: minimal clinically important difference [published correction appears in Mov Disord. 2019;34(11):1753-1754]. Mov Disord. 2019;34(8):1203-1209. doi:10.1002/mds.27769
Pardis P, Remington G, Panda R, Lemez M, Agid O. Clozapine and tardive dyskinesia in patients with schizophrenia: a systematic review. J Psychopharmacol. 2019;33(10):1187-1198. doi:10.1177/0269881119862535
Prescribers’ Digital Reference. Clozapine- drug summary.
Food and Drug Administration. Atypical antipsychotic drugs information.
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