What is Clozapine?

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  • Written By: Christian Petersen
  • Edited By: Susan Barwick
  • Last Modified Date: 20 September 2019
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Clozapine is an anti-psychotic drug used to treat schizophrenia. It belongs to a class of drugs called atypical anti-psychotics and is the first drug of this type to be developed. Clozapine has the chemical formula C18H19ClN4. It was first synthesized in 1961, and its first recorded use was in Europe in 1971. It proved to be somewhat dangerous due to a tendency to cause a blood disorder called agranulocytosis and was recalled from use in 1975. Today it is in use again in combination with monitoring in the form of regular blood tests.

At least three drug companies distribute clozapine today; Novartis, which manufactures the drug, and two companies who only market it — Mylan Laboratories and Ivax Pharmaceuticals. Other companies may also market generic versions of the drug. It is sold under brand names which vary in different parts of the world, including Clozaril®, Clopine, Denzapine, Klozapol and others.


This drug is considered to be highly effective for the treatment of schizophrenia but is used as an option of last resort due to its associated dangers. It is only prescribed for treatment-resistant schizophrenia, which is defined as schizophrenia which does not respond to at least two other less dangerous drugs. In the United States, the US Food and Drug Administration (FDA) requires clozapine packaging to be labeled with warnings for many potentially dangerous side effects besides agranulocytosis, such as seizures, myocarditis, bone marrow suppression, and dementia, among others. Several less severe side effects include drooling, constipation, muscle tremors, tardive dyskinesia, and weight gain.

Despite its dangers, clozapine is still used to treat cases of schizophrenia that do not respond to other drugs. It is effective in treating several symptoms associated with the disorder. Schizophrenia symptoms are generally grouped into two categories: positive and negative. Positive symptoms include hallucinations and delusions. Negative symptoms include social withdrawal and emotional isolation.

Clozapine is known to treat both positive and negative symptons, and unlike many other psychoactive drugs, can actually increase a patient's clarity of thought and perception of reality. There are other uses for this drug, but they are considered "off-label" or in the experimental or testing stages. Patients with bipolar disorder, chronic insomnia, schizoid personality disorder, and a specific type of dementia called Lewy-body dementia may benefit from clozapine, but these uses are not approved in most parts of the world, including the United States and Europe.

Patients with other conditions should not take clozapine. Epileptics, patients with a muscle disorder called myeloproliferative disease, and patients with liver damage or cardiovascular damage are considered to be at too high of a risk for serious health problems. The drug is also known to interact with other drugs, including fluvoxamine and benzodiazepines, in an unfavorable way.


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