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Clozaril Warnings and Precautions

Specific Clozaril Warnings and Precautions

Warnings and precautions to be aware of before starting treatment with Clozaril include the following:
  • Clozaril can cause agranulocytosis, a life-threatening condition involving very low levels of white blood cells. In order to detect this problem early, frequent blood tests are required for people taking the medication. For the first six months, you will need blood tests weekly; from 6 to 12 months, the tests are required every two weeks. After one year (and until you stop taking Clozaril), the test can be given just once a month.
  • Studies have shown that Clozaril can increase the risk of seizures. The higher the dose of Clozaril, the greater the risk.
  • The medication can increase the risk of life-threatening myocarditis (inflammation of the heart). If your healthcare provider suspects you may have myocarditis, you should stop taking Clozaril immediately.
  • Clozaril can cause a drop in blood pressure when going from a sitting or lying-down position to standing (known medically as orthostatic hypotension). This can cause a person to have lightheadedness or dizziness, or to faint. Tell your healthcare provider if you have any of these symptoms when standing. Orthostatic hypotension can be especially dangerous in people with heart disease or congestive heart failure (CHF).
  • The U.S. Food and Drug Administration (FDA) has issued a special warning (a "black box warning") about the use of the drug in elderly people with dementia (a condition involving confusion; disorientation; and a loss of memory, intellect, and judgment) or psychosis.
Elderly people with dementia (Alzheimer's disease is the most common form) who are treated with atypical antipsychotics -- including Clozaril -- are more likely to die of various causes than those who were not treated with those medications. Clozaril is not approved to treat dementia in the elderly, and caution should be used before giving the drug to elderly people with dementia.
  • Clozaril can cause an irregular heart rhythm (arrhythmia) or other heart problems. If you already have an arrhythmia or heart problem, your healthcare provider should monitor you very closely during treatment.
In some cases, Clozaril has caused a specific type of arrhythmia called QT prolongation, which can be quite dangerous. People with long QT syndrome should probably not take Clozaril. People taking certain other medications, people with certain electrolyte balances, and people with heart disease may also be at an increased risk for QT prolongation with this medication.
  • Clozaril can cause a life-threatening condition called neuroleptic malignant syndrome (NMS). Symptoms of NMS include:
    • A high fever
    • Stiff muscles
    • Confusion
    • An irregular pulse or blood pressure
    • A fast heart rate (tachycardia)
    • Sweating
    • An irregular heart rhythm (arrhythmia).


Tell your healthcare provider right away if think you might have NMS.
  • Clozaril can cause tardive dyskinesia, a condition involving unusual, uncontrollable body or facial movements. The condition can become permanent even if Clozaril is stopped. The best way to prevent it from becoming permanent is to tell your healthcare provider right away if you notice any abnormal movements (including abnormal movements of the tongue) while taking the drug.
  • Clozaril can cause an increase in blood sugar levels and can increase the risk of developing diabetes. Tell your healthcare provider if you develop signs of diabetes while taking it. Possible signs include an increase in thirst, urination, or hunger. If you have diabetes, your blood sugar should be monitored carefully and regularly during treatment with Clozaril to make sure the condition is not becoming more severe (see Clozapine and Diabetes).
  • In addition to diabetes, Clozaril may increase the risk for excessive weight gain and high cholesterol.
  • Be sure to tell your healthcare provider if you have liver disease, glaucoma, severe constipation, or an enlarged prostate. Clozaril can make these conditions worse.
  • If you have an upcoming surgery, it is important for your surgeon and anesthesiologist to know that you are taking Clozaril.
  • Clozaril can cause drowsiness and may impair your ability to drive or operate heavy machinery. Make sure you know how the medication will affect you before doing anything that requires concentration and motor skills.
  • Clozaril is considered a pregnancy Category B medication. This means that it is probably safe for pregnant women, although the full risks are not known. Be sure to talk with your healthcare provider about the risks and benefits of using the drug during pregnancy (see Clozapine and Pregnancy).
  • Clozaril can interact with other medications (see Clozaril Drug Interactions).
  • Clozaril passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Clozapine and Breastfeeding).
  • In general, alcohol should be avoided while taking Clozaril (see Alcohol and Clozapine).
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