Precautions and Warnings With Clozapine

Specific Precautions and Warnings With Clozapine

Warnings and precautions to be aware of prior to taking clozapine include the following:
  • Clozapine 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 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 clozapine), the test can be given just once a month.
  • Studies have shown that the medication increases the risk of seizures. The higher the dose of clozapine, the greater the risk.
  • Clozapine can increase the risk of life-threatening myocarditis (inflammation of the heart). If your healthcare provider suspects that you may have myocarditis, you should stop taking the drug immediately.
  • Clozapine 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 clozapine 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 clozapine -- are more likely to die of various causes than those who were not treated with those medications. Clozapine is not approved to treat dementia in the elderly, and caution should be used before giving the medication to elderly people with the condition.
  • Clozapine 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, clozapine has caused a specific type of arrhythmia called QT prolongation, which can be quite dangerous. People with long QT syndrome should probably not take clozapine. 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 drug.

  • The medication can cause a life-threatening condition called neuroleptic malignant syndrome (NMS). Some 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.
  • Clozapine can cause tardive dyskinesia, a condition involving unusual, uncontrollable body or facial movements. The condition can become permanent even if clozapine 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.
  • Clozapine 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 the drug. Possible signs can include an increase in thirst, urination, or hunger. If you have diabetes, your blood sugar should be monitored carefully and regularly during treatment with clozapine to make sure that it is not becoming more severe (see Clozapine and Diabetes).
  • In addition to diabetes, clozapine 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, as clozapine 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 clozapine.
  • The medication can cause drowsiness and may impair your ability to drive or operate heavy machinery. Make sure you know how clozapine will affect you before doing anything that requires concentration and motor skills.
  • Clozapine 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 taking the drug when pregnant (see Clozapine and Pregnancy).
  • Clozapine can interact with other medications (see Drug Interactions With Clozapine).
  • Clozapine passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking it (see Clozapine and Breastfeeding).
  • Alcohol should generally be avoided while taking clozapine (see Alcohol and Clozapine).
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