phenothiazine fēˌnəthīˈəzĭn [key], any one of a class of drugs used to control mental disorders. Phenothiazines, along with other antipsychotic, or neuroleptic, drugs are used for such disorders as schizophrenia, paranoia, mania, psychosis resulting from mental deficiency, some forms of senility, hyperactivity in children, and even severe anxiety. Phenothiazines reduce psychiatric disorders without causing addiction or euphoria; sedation usually only occurs in the early stages of drug therapy. The most widely used phenothiazine, chlorpromazine (Thorazine), is prescribed for overactive schizophrenics; trifluoperazine (Stelazine) is used for inhibited and withdrawn schizophrenics. Typically, when a phenothiazine is taken over long periods of time, the frequency of recurring schizophrenic episodes decreases. Other phenothiazines are used in anesthesia and to control itching. Although many patients on phenothiazines and other neuroleptics show marked improvement, these drugs, when used over long periods of time, are fairly toxic. Parkinsonism (see Parkinson's disease) is a well-known side effect. Some patients experience severe reduction of motor activity, abnormal skin pigmentation, and visual impairment. Chlorpromazine therapy is associated with jaundice. Because many phenothiazines are potent anti-emetics, i.e., they control vomiting, they may mask symptoms of toxic drug overdosage or of pathological disorders such as brain tumors. Phenothiazines also cause a disorder called tardive dyskinesia, which consists of bizarre muscular movements such as lip smacking and abnormal postures. It occurs in patients who have been given the drug for long periods of time. See also psychopharmacology.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.

See more Encyclopedia articles on: Pharmacology