Neuroleptics(redirected from major tranquillizers)
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(also called neuroplegics, antipsychotics, major tranquilizers), a group of pharmacologically active substances that exert a unique depressive influence on many functions of the nervous system.
Neuroleptics are sedatives that effect an indifferent attitude in the patient toward the surroundings, a decrease in motor activity and in skeletal muscle tonus, a weakening of autonomic reactivity (which tends to be accompanied by a decrease in body temperature), a lowering of arterial blood pressure, and a weakening of reflexes from the internal organs. Neuroleptics intensify the action of narcotics, somnifacients, analgesics, and anesthetics, and they weaken the action of stimulators of nervous activity, such as caffeine and phenamine. Neuroleptic substances also have antiemetic properties.
As a result of the influence of neuroleptics on the central nervous system, changes in mental activity and emotional state arise without disturbances of consciousness. These changes are accompanied by fluctuations in the electrical biopotentials of the brain. The antipsychotic action, which is especially characteristic of neuroleptics, accounts for the successful treatment of psychomotor excitement and mental disorders, such as delirium, hallucination, or anxiety. The first neuroleptic, chlorpromazine, was studied by the French pharmacologist F. Courvoisier in the early 1950’s; somewhat later, reserpine was introduced into therapy as a neuroleptic.
Structurally, neuroleptics belong to various classes of chemical compounds; of the greatest practical importance are the derivatives of phenothiazine, thioxanthene, butyrophenone, and indole. Although the mechanism of action has not been sufficiently studied, it is known that neuroleptics influence the transmission of nerve impulses within the synapses of various brain structures. It is also known that neuroleptics suppress the activating influence of the reticular formation of the brain on the cerebral cortex and lower the activity of mediator substances (chemical transmitters), which brings about a change in the functional activity of the brain.
Neuroleptics opened up a new era in the treatment of various mental diseases, for example, schizophrenia and manic-depressive psychosis; they have also been widely used in combination with narcotics and analgesics to eliminate pain during surgery. Neuroleptics have broad application to the clinical practice of internal medicine, especially in the treatment of hypertension, ulcers, and ischemic diseases of the heart; they are also used against itching in skin diseases and as antiemetics in pernicious vomiting of pregnancy.
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V. V. ZAKUSOV