Medically reviewed by Drugs.com. Last updated on Dec 23, 2021.
Severe Neutropenia; Orthostatic Hypotension; Bradycardia, and Syncope; Seizure; Myocarditis and Cardiomyopathy; Increased Mortality in Elderly Patients with Dementia-related PsychosisSevere Neutropenia: Clozapine can cause severe neutropenia, which can lead to serious and fatal infections. Patients initiating and continuing treatment with clozapine must have a baseline blood absolute neutrophil count (ANC) measured before treatment initiation and regular ANC monitoring during treatment.Clozapine is available only through a restricted program called the Clozapine Risk Evaluation Mitigation Strategy (REMS).Orthostatic Hypotension, Bradycardia, and Syncope: Risk is dose related. Starting dose is 12.5 mg. Titrate gradually and use divided dosages.Seizure: Risk is dose-related. Titrate gradually and use divided doses. Use with caution in patients with history of seizure or risk factors for seizure.Myocarditis, Cardiomyopathy and Mitral Valve Incompetence: Can be fatal. Discontinue and obtain cardiac evaluation if findings suggest these cardiac reactions.Increased Mortality in Elderly Patients with Dementia-Related Psychosis: Clozapine is not approved for this condition .
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
- Tablet, Disintegrating
Therapeutic Class: Antipsychotic
Chemical Class: Dibenzodiazepine
Uses for clozapine
Clozapine is used to treat severely ill patients with schizophrenia who have used other medicines that did not work well. It is also used to lower risk of suicidal behavior in patients with schizophrenia or schizoaffective disorder. Clozapine changes some of the chemicals in the brain that are thought to cause schizophrenia. Clozapine should not be used to treat behavioral problems in older adults with dementia.
Clozapine is only available through a restricted program. You might be asked to read and sign papers that explain how the medicine works and some of the unwanted effects.
Before using clozapine
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For clozapine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to clozapine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of clozapine in the pediatric population. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of clozapine in the elderly. However, elderly patients are more likely to have constipation, trouble passing urine, uncontrolled movements, or age-related liver, kidney, or heart problems, which may require caution in patients receiving clozapine.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking clozapine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using clozapine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- Potassium Citrate
Using clozapine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Abiraterone Acetate
- Aripiprazole Lauroxil
- Arsenic Trioxide
- Calcium Oxybate
- Doxorubicin Hydrochloride Liposome
- Gabapentin Enacarbil
- Glycopyrronium Tosylate
- Inotuzumab Ozogamicin
- Interferon Alfa-2b
- Magnesium Oxybate
- Morphine Sulfate Liposome
- Oxitropium Bromide
- Peginterferon Alfa-2a
- Pipenzolate Bromide
- Potassium Oxybate
- Ropeginterferon Alfa-2b-njft
- Secretin Human
- Sodium Oxybate
- Sodium Phosphate
- Sodium Phosphate, Dibasic
- Sodium Phosphate, Monobasic
- St John's Wort
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using clozapine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use clozapine, or give you special instructions about the use of food, alcohol, or tobacco.
- Grapefruit Juice
Using clozapine with any of the following may cause an increased risk of certain side effects but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use clozapine, or give you special instructions about the use of food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of clozapine. Make sure you tell your doctor if you have any other medical problems, especially:
- Alcohol abuse, history of or
- Blood clotting problems (eg, deep vein thrombosis, pulmonary embolism) or
- Blood vessel problems (poor circulation) or
- Dehydration or
- Head injury, history of or
- Heart attack, recent or history of or
- Heart disease (eg, cardiomyopathy, myocarditis) or
- Heart failure or
- Heart rhythm problems (eg, arrhythmia, long QT syndrome, slow heart rate), or history of or
- Hypokalemia (low potassium in the blood) or
- Hypomagnesemia (low magnesium in the blood) or
- Hypotension (low blood pressure) or
- Hypovolemia (low blood volume) or
- Stroke, history of—May cause side effects to become worse.
- Diabetes or
- Difficult urination or
- Dyslipidemia (high cholesterol or fat in the blood) or
- Enlarged prostate or
- Glaucoma, narrow angle or
- Hyperglycemia (high blood sugar) or
- Liver disease (eg, hepatitis) or
- Neuroleptic malignant syndrome, history of or
- Seizures, history of or
- Stomach or bowel problems (eg, constipation)—Use with caution. May make these conditions worse.
- Kidney disease or
- Liver disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
- Phenylketonuria (PKU)—The orally disintegrating tablet contains phenylalanine, which can make this condition worse.
Proper use of clozapine
Take clozapine only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. Do not miss any doses.
Clozapine comes with a patient instructions. Read and follow the instructions carefully. Ask your doctor if you have any questions.
Take the oral liquid or tablet with or without food.
If you are using the disintegrating tablet, make sure your hands are dry before you handle the tablet. Do not open the blister pack that contains the tablet until you are ready to take it. Remove the tablet from the blister pack by peeling back the foil, then taking the tablet out. Do not push the tablet through the foil. Place the tablet in your mouth. It should melt quickly. After the tablet has melted, swallow or chew it as desired.
Shake the bottle of the oral liquid for 10 seconds before each use. Measure the dose with the dosing syringe that comes with the package. Wash the oral syringe with warm water after using it.
Drink plenty of fluids with clozapine to help prevent constipation.
The dose of clozapine 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 clozapine. 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.
- For oral dosage forms (disintegrating tablets, suspension, or tablets):
- For schizophrenia or prevention of suicidal behavior:
- Adults—At first, 12.5 milligrams (mg) per day, taken as a single dose or two times per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 900 mg per day.
- Children—Use and dose must be determined by your doctor.
- For schizophrenia or prevention of suicidal behavior:
If you miss a dose of clozapine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
If you miss 2 or more days of clozapine doses, talk to your doctor before you start taking it again. You might have to restart the medicine at a lower dose than you were taking before.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Do not refrigerate or freeze the oral liquid. Throw away any unused medicine 100 days after opening the bottle for the first time.
Precautions while using clozapine
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 clozapine 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 clozapine affects you.
Clozapine 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 clozapine, 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.
Clozapine 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: Clozapine 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 clozapine.
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).
Clozapine 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 clozapine: 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 clozapine 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.
Clozapine 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 clozapine.
Make sure any doctor or dentist who treats you knows that you are using clozapine. You may need to stop using clozapine 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.
Clozapine side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- Blurred vision
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- fast, pounding, or irregular heartbeat or pulse
- shakiness in the legs, arms, hands, or feet
- sleepiness or unusual drowsiness
- trembling or shaking of the hands or feet
- unusual tiredness or weakness
- black, tarry stools
- chest pain
- cough or hoarseness
- decrease in the frequency of urination
- decrease in urine volume
- difficult or labored breathing
- difficulty in passing urine (dribbling)
- dry mouth
- feeling sad or empty
- fever with or without chills
- frequent strong or increased urge to urinate
- general feeling of tiredness or weakness
- lack of appetite
- loss of bladder control
- loss of interest or pleasure
- lower back or side pain
- muscle spasm or jerking of the arms or legs
- painful or difficult urination
- pounding in the ears
- restlessness or need to keep moving
- severe or continuing headache
- shakiness and unsteady walk
- slurred speech
- sore throat
- sores, ulcers, or white spots on the lips or in the mouth
- sudden jerky movements of the body
- sudden loss of consciousness
- swollen glands
- throat discomfort
- tightness in the chest
- trouble concentrating
- trouble sleeping
- unsteadiness, trembling, or other problems with muscle control or coordination
- Absence of or decrease in movement
- change in appetite
- dark urine
- decreased sexual ability
- difficult or fast breathing or sudden shortness of breath
- increased sweating
- increased thirst
- increased urination
- lip smacking or puckering
- muscle stiffness (severe)
- puffing of the cheeks
- rapid or worm-like movements of the tongue
- swelling or pain in the leg
- uncontrolled chewing movements
- uncontrolled movements of the arms and legs
- unusual bleeding or bruising
- unusually pale skin
- yellow eyes or skin
Incidence not known
- burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
- clay-colored stools
- confusion as to time, place, or person
- epileptic seizure that will not stop
- feeling that others are watching you or controlling your behavior
- feeling that others can hear your thoughts
- feeling, seeing, or hearing things that are not there
- holding false beliefs that cannot be changed by fact
- inability to move the eyes
- increased blinking or spasms of the eyelid
- itching or skin rash
- joint pain
- light-colored stools
- muscle twitching
- pains in the stomach, side, or abdomen, possibly radiating to the back
- rhythmic movement of the muscles
- severe mood or mental changes
- sticking out of the tongue
- swelling around the eyes
- swelling of the body or feet and ankles
- trouble with speaking
- unpleasant breath odor
- unusual behavior
- unusual excitement, nervousness, or restlessness
- unusual facial expressions
- unusual weight gain
- upper right abdominal or stomach pain
- vomiting of blood
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Acid or sour stomach
- feeling of constant movement of self or surroundings
- relaxed and calm sensation of spinning
- Blurred or loss of vision
- change or problem with discharge of semen
- disturbed color perception
- double vision
- halos around lights
- inability to sit still
- increase in body movements
- muscle ache or pain
- muscle weakness
- night blindness
- overbright appearance of lights
- pain in the back, neck, or legs
- pain in the chest below the breastbone
- severe muscle stiffness
- sore tongue
- stuffy nose
- tunnel vision
- unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
Incidence not known
- Blistering, peeling, or loosening of the skin
- hives, sores, welting, or blisters
- increased sensitivity of the skin to sunlight
- painful or prolonged erection of the penis
- red skin lesions, often with a purple center
- red, irritated eyes
- reddening of the skin, especially around the ears
- severe stomach pain
- severe sunburn
- swelling of the eyes, face, or inside of the nose
- swelling of the salivary glands
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
More about clozapine
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- During pregnancy or Breastfeeding
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- Drug class: atypical antipsychotics
- Drug Information
- Clozapine Oral Suspension
- Clozapine Orally Disintegrating Tablets
- Clozapine Tablets
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