Clozapine (Clozaril) is used to treat schizophrenia. It's an atypical antipsychotic, but it's not a first-choice medication for schizophrenia because it can cause many bothersome side effects, such as drowsiness and dizziness. It can also cause your white blood cell (WBC) count to drop dangerously low and raise your risk for serious infections. As a result, clozapine (Clozaril) is prescribed under a special program called Risk Evaluation and Mitigation Strategies (REMS). In order to pick up your medication at the pharmacy, your provider will ask you to get blood work regularly (weekly to monthly) to make sure your WBC count is at a healthy level.
Schizophrenia that hasn't responded to other treatments
Suicidal behavior in people with schizophrenia or schizoaffective disorder
Clozapine (Clozaril) is a second generation "atypical" antipsychotic. It's not exactly known how it works, but it mainly targets and changes dopamine and serotonin activity in your brain, which affect your thoughts, behavior, and mood.
Source:Â DailyMed
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:
More common
Blurred vision
confusion
dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
fainting
fast, pounding, or irregular heartbeat or pulse
shakiness in the legs, arms, hands, or feet
sleepiness or unusual drowsiness
sweating
trembling or shaking of the hands or feet
unusual tiredness or weakness
vomiting
Less common
black, tarry stools
chills
convulsions
cough or hoarseness
decrease in the frequency of urination
decrease in urine volume
difficult or labored breathing
difficulty in passing urine (dribbling)
discouragement
feeling sad or empty
fever with or without chills
frequent strong or increased urge to urinate
general feeling of tiredness or weakness
headache
hyperventilation
irritability
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
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
Rare
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
weakness
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
indigestion
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:
More common
Acid or sour stomach
belching
feeling of constant movement of self or surroundings
relaxed and calm sensation of spinning
sleepiness
Less common
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
nightmares
overbright appearance of lights
pain in the back, neck, or legs
pain in the chest below the breastbone
severe muscle stiffness
sore tongue
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.
Works well to treat schizophrenia when other medications haven't worked well
Taken by mouth
Comes as both a regular tablet (that you swallow by mouth) and as a dissolvable tablet that you place on the tongue
Available as a lower-cost generic
Need to get blood work done every time you get a prescription filled (weekly to monthly)
Can cause dizziness and drowsiness
Can cause high blood sugar, high cholesterol, and weight gain
Not a good option for people with a history of seizures
You can take clozapine (Clozaril) with or without food because food doesn't affect how well this medication works.
Take clozapine (Clozaril) exactly as prescribed and don't stop taking it without talking to your healthcare provider. Stopping it all of a sudden can cause your symptoms to return, or you could have withdrawal symptoms such as sweating, headache, nausea, vomiting, and diarrhea.
To avoid feeling dizzy while taking this medication, rise slowly if you have been sitting or lying down. Avoid driving and other tasks that require you to be alert until you know how clozapine (Clozaril) affects you.
Clozapine (Clozaril) is part of a special monitoring program called the clozapine (Clozaril) REMS Program because of its risk for low white blood cells and infection. You'll need to get blood tests before you start this medication and before every refill. You must pick up the medication within 7 days of your blood tests.
If you miss taking clozapine (Clozaril) for more than 2 days, don't just restart it; call your provider for guidance on what to do. Your provider will likely ask you to start clozapine (Clozaril) at a lower dose and raise your dose slowly over time until you get to the dose you were taking before.
You might experience constipation while taking clozapine (Clozaril). You should drink plenty of water and eat foods with enough fiber. If you continue to pass less than 3 stools a week, you will need to contact your healthcare provider.
There are many medication interactions with clozapine (Clozaril). Certain medications can make clozapine (Clozaril) not work as well (e.g., phenytoin), while others can cause clozapine (Clozaril) levels to go too high which can cause serious side effects (e.g., bupropion). Let your healthcare provider and pharmacist know all the medications, including vitamins and herbal supplements you're taking.
Clozapine (Clozaril) might affect your weight, cholesterol, and blood sugar control. You will need to get these checked regularly while you taking this medication.
Let your healthcare provider know if you are pregnant, planning on becoming pregnant or breastfeeding while taking this medication.
If you're taking the orally disintegrating tablet, place the tablet on your tongue right after removing it from the blister pack. You don't need to swallow water afterwards, your regular saliva is enough.
Clozapine (Clozaril) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Clozapine (Clozaril) can cause low neutrophil (white blood cell, or WBC) count, which can lead to serious infections. Due to this risk, clozapine (Clozaril) is only available under a restricted program called the clozapine (Clozaril) REMS Program, which ensures that healthcare providers and pharmacies have the appropriate training to prescribe and dispense this medication. Your provider will measure your neutrophil level before you start clozapine (Clozaril) to make sure it's not too low. In addition, you'll need to get regular blood tests (weekly to monthly) while you're receiving treatment. You'll only be able to pick up your clozapine (Clozaril) prescription at the pharmacy if your neutrophil levels are within a safe range. Let your healthcare provider know right away if you experience symptoms of an infection, such as fever, weakness, sore throat, or cough while taking this medication.
Risk factors: History of heart-related conditions, such as heart attack | Dehydration | Taking blood pressure medications | Heart failure
Clozapine (Clozaril) can cause low blood pressure and a slower heartbeat, which can lead to fainting or falling. This is most likely to happen if you're starting this medication for the first time or any time your provider is raising your dose too quickly. Your risk of these side effects is higher if you're also taking blood pressure medications or if you're dehydrated. To lower your risk of low blood pressure or falls, your provider will raise your dose of clozapine (Clozaril) slowly over time. Make sure to also drink enough of liquids to stay hydrated throughout the day. Contact to your healthcare provider if you feel dizzy or lightheaded.
Risk factors: Seizure disorder | Drinking large amounts of alcohol regularly | Taking medications that raise the risk for seizures | Head injury
People taking clozapine (Clozaril) have reported having seizures. The risk for seizures is higher for people who are taking higher doses of clozapine (Clozaril) or who are taking other medications that can raise the risk for seizures. Let your caregiver or family members know of this risk and teach them how they can help if you have a seizure. Be careful driving, swimming, or participating in other potentially dangerous activities in which sudden loss of consciousness could cause serious harm. Talk to your healthcare provider if you have a history of seizures.
Risk factors: History of heart problems
People taking clozapine (Clozaril) have reported issues with their heart muscles, which can be serious and sometimes life-threatening. If you experience these problems, your provider will switch you to a different medication, unless they think the benefit of clozapine (Clozaril) is greater than the risk of harm. Call your healthcare provider right away if you have chest pain or pressure, a heartbeat that doesn't feel normal, trouble breathing, fainting, or fever.
Risk factors: Ages 65 years and older
People ages 65 years and older with dementia sometimes have delusions and hallucinations (believing, seeing, or hearing things that aren't real). This is called dementia-related psychosis. Older people with dementia-related psychosis have a higher risk of death if they take medications like clozapine (Clozaril). Because of this risk, clozapine (Clozaril) shouldn't be used in people 65 years and older with dementia-related psychosis. Let your provider know if you or someone you know has dementia before starting clozapine (Clozaril).
Clozapine (Clozaril) can raise your blood sugar and cholesterol levels as well as raise your appetite, all of which can lead to weight gain. Your provider will likely order blood tests regularly throughout treatment with clozapine (Clozaril) to make sure your blood sugar and cholesterol aren't too high. Make sure to have a healthy and balanced diet low in fat and sugar and maintain a regular exercise routine while taking clozapine (Clozaril).
Some people taking clozapine (Clozaril) experienced severe constipation and other gut-related problems. This is because this medication can cause your gut muscles to move more slowly, which can cause stool to get backed up in the intestines or other complications. You should drink plenty of fluids and eat a fiber-full diet while taking clozapine (Clozaril) to lower your risk of gut-related problems. If your passing less than 3 stools a week or if you have symptoms such as nausea, vomiting, or stomach pain, ask your provider if you need more medical attention.
Clozapine (Clozaril) can cause eosinophil levels (a type of white blood cell) to rise. This can lead to a reaction called drug reaction with eosinophilia and systemic symptoms syndrome (DRESS), which can in turn, lead to problems in other organs in your body, such as the heart, pancreas, and kidneys. Let your provider know right away if you have a fever, rash, or swollen lymph nodes.
Risk factors: Low potassium or magnesium blood levels | Older age | Female sex | Using other medications that cause QT prolongation | Born with QT prolongation | Hypothyroidism (low thyroid hormone) | History of heart problems or abnormal heart rhythms (arrhythmias) | Slow heart rate
Although rare, clozapine (Clozaril) can affect your heart rhythm by lengthening the time period from when the heart pumps and then relaxes. This is known as QT prolongation and it can be life-threatening. Your risk for QT prolongation is higher if you have any of the risk factors listed above. To lower your risk of QT prolongation, your provider will periodically monitor you and draw labs to make sure your numbers are normal. Make sure to tell your provider about all the medications you're taking and don't start any new medications while taking clozapine (Clozaril) without talking to your provider or pharmacist first. People who were born with QT prolongation or have a history of arrhythmias should avoid taking clozapine (Clozaril). If you feel your chest pounding, have trouble breathing, chest pain, or feel faint or lightheaded while taking clozapine (Clozaril), call 911 right away.
This is a rare, but life-threatening condition associated with antipsychotic medications. Symptoms include high fever, fast heart rate, full body stiffness, and confusion. Get medical attention right away if you notice any of these symptoms. Your healthcare provider will likely find you another medication that will work better for you.
Risk factors: Drinking alcohol | Taking other medicines that make you less alert
Clozapine (Clozaril) impairs your ability to focus, think, and react. Be careful and avoid driving a car or other activities that require mental concentration until you know how this medication affects you.
Risk factors: History of liver disease like hepatitis
Rare, but life-threatening, liver problems can happen in people who take clozapine (Clozaril). Your healthcare provider might check your liver health with blood tests and checkups while you're taking this medication. If you do experience any severe abdominal pain, dark urine, weakness, yellowing of skin or eyes you should let your healthcare provider know right away.
Risk factors: Taking other antipsychotic medications | High dose | Taking clozapine (Clozaril) for a long period of time
Antipsychotic medications like clozapine (Clozaril) can cause uncontrolled body movements, such as eye-twitching or lip-smacking. Your risk of this happening is higher the longer you take medications like clozapine (Clozaril) and if you're taking a higher dose. These movement problems can become permanent. To lower your risk of movement problems, your provider will prescribe the lowest dose of clozapine (Clozaril) you need to treat your symptoms. If you experience any uncontrolled movements and aren't able to stop them, talk to your provider right away.
If you have a condition called phenylketonuria, let your provider know. The dissolvable clozapine tablets contain phenylalanine, which can build up in your body and cause health problems.
The typical starting dose is 12.5 mg by mouth once or twice daily. Your provider might raise your dose slowly over time, depending on your symptoms and blood work. The typical recommended dosing range is 300 mg to 450 mg total daily, split into smaller doses and taken throughout the day. The maximum total daily dose is 900 mg.
Using this medicine 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.
Using this medicine 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.
Schizophrenia that hasn't responded to other treatments
Suicidal behavior in people with schizophrenia or schizoaffective disorder
Tourette syndrome in children
Depression (add-on treatment)
Irritability associated with autistic disorder in children
Schizophrenia in adults and children age 13 years and older
Bipolar I disorder in adults and children age 13 years and older
Bipolar depression in adults and children age 10 years and older
Depression that hasn't responded well to other treatments
By signing up, I agree to GoodRx's Terms and Privacy Policy, and to receive marketing messages from GoodRx.
Accord Healthcare Inc. (2023). Clozapine tablet [package insert]. DailyMed.
Clozapine REMS. (n.d.). What is the clozapine REMS?
Correll, C. U., et al. (2022). A guideline and checklist for initiating and managing clozapine treatment in patients with treatment-resistant schizophrenia. Central Nervous System Drugs.
Hallare, J., et al. (2023). Half life. StatPearls.
Holder, S. D., et al. (2014). Schizophrenia. American Family Physician.
MedlinePlus. (n.d.). Phenylketonuria.
MGH Center for Women’s Mental Health. (n.d.). National Pregnancy Registry for Psychiatric Medications©.
Mylan Institutional Inc. (2022). Clozapine tablet, orally disintegrating [package insert]. DailyMed.
Rosenheck, R., et al. (1999). How long to wait for a response to clozapine: A comparison of time course of response to clozapine and conventional antipsychotic medication in refractory schizophrenia. Schizophrenia Bulletin.
Research prescriptions and over-the-counter medications from A to Z, compare drug prices, and start saving.