Psychopharmacology (redirected from psychopharmacological)

psychopharmacology (sī'kōfär'məkŏl`əjē), in its broadest sense, the study of all pharmacological agents that affect mental and emotional functions. The term is usually applied more specifically to the study and synthesis of drugs used in the control of psychiatric illnesses, namely the antipsychotic, antianxiety, antidepressant, and antimanic medications. The widespread use of drugs among individuals suffering from mental illness is a relatively recent phenomenon, developing since the 1950s.

Antipsychotic Drugs

Antipsychotic drugs can ameliorate the types of delusions and hallucinations characteristic of bipolar disorder (see depression) and schizophrenia. The first drug of this type was reserpine, whose use dates from ancient Hindu medicine but whose reintroduction as an antipsychotic agent in 1954 marked the beginning of the large-scale use of antipsychotic drugs. Because of side effects, including depression, reserpine has been supplanted by phenothiazine drugs. The phenothiazine chlorpromazine (Thorazine) was the first to be widely applied to mental disorders and remains one of the standard drugs. Drugs of the phenothiazine family are most useful in the treatment of schizophrenia. They are thought to act in part by blocking dopamine receptors at the synapse, reducing brain activity. The phenothiazines and clozapine have been credited with a revolutionary transformation of mental health care, enabling increasing numbers of psychotic persons to function outside the hospital. Antipsychotic drugs may have negative side effects, such as the dulling of physical and mental functioning, tardive dyskinesia, and sedation.

Antianxiety Drugs

Antianxiety drugs, including the propanediol meprobamate (Miltown or Equanil), and the more recent benzodiazephines—such as diazepam (Valium)—have found wide use in reducing tension and anxiety among individuals with less serious mental disorders, but may lead to addiction if abused. Although they form a chemically diverse group, the physiological effects of each are similar; in small doses they relieve anxiety by reducing muscular tension, and in larger doses they produce sedation, sleep, and anesthesia (see depressant). Antianxiety drugs are the most frequently prescribed pharmaceuticals in the United States.

Antidepressants

Antidepressants appeared in the late 1950s, and have been used in the treatment of individuals suffering from major depression or the depression phase of bipolar disorder. Antidepressants include the tricyclics and monoamine oxidase (MAO) inhibitors. These drugs have the effect of increasing the concentration in the nervous system of catecholamines such as epinephrine. The toxic effects of the MAO inhibitors have been largely overcome in recent years, and the drugs are still used in many instances. They have been supplanted in many uses, however, by tricyclic compounds, such as amitriptyline (Elavil), and the newer serotonin increasers, such as fluoxetine (Prozac) and sertraline HCL (Zoloft). Tricyclics are chemically similar to phenothiazines, but that activate rather than tranquilize (see stimulant). The choice of an antidepressant often has more to do with its side effects than efficacy.

Antimanic and Hallucinogenic Drugs

The element lithium, in the form lithium carbonate, has been widely used as an antimanic in cases of bipolar disorder (manic-depression), particularly to control manic episodes. Lithium alters the transport of sodium ions in nerve and muscle cells and affects the metabolism of catecholamines; the exact mechanism of action is unknown. The hallucinogenic drugs, such as mescaline and LSD, have been of research interest because they often mimic natural psychotic states.

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psychopharmacology

Study of the effect of drugs on the mind and behaviour, particularly in the context of developing treatments for mental disorders. Major psychopharmacological advances in the 20th century include the development of tranquilizers, antidepressants, lithium carbonate (for bipolar disorder), certain stimulants (including amphetamines), and antipsychotic agents such as chlorpromazine (Thorazine), fluphenazine (Prolixin), and haloperidol (Haldol).

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Psychopharmacology

A discipline that merges the subject matter of psychology, which studies cognition, emotion, and behavior, and pharmacology, which characterizes different drugs. Thus, psychopharmacology focuses on characterizing drugs that affect thinking, feeling, and action. In addition, psychopharmacology places particular emphasis on those drugs that affect abnormalities in thought, affect, and behavior, and thus has a relationship to psychiatry. Psychopharmacology is predominantly, but not exclusively, concerned with four major classes of drugs that are of clinical significance in controlling four major categories of psychiatric disorder: anxiety, depression, mania, and schizophrenia.

Anxiety is an emotional state that can range in intensity from mild apprehension and nervousness to intense fear and even terror. It has been estimated that 2–4% of the general population suffer from an anxiety disorder at some time. Although anxiety in some form is a common experience, it can become so intense and pervasive as to be debilitating; it may therefore require psychiatric attention and treatment with an anxiolytic drug. There are three major groups of anxiolytics. Members of the first group are called propanediols; meprobamate is the most widely used. The second group is the barbiturates, of which phenobarbital is the most generally prescribed. The third group, most frequently prescribed, is the benzodiazepines, the best known of which is diazepam.

A major advance in understanding the benzodiazepines was the identification of the cellular sites at which these drugs act (so-called benzodiazepine receptors). The distribution of these receptors in the brain has also been found to have a striking parallel to the distribution of the receptors for a naturally occurring substance called gamma-amino butyric acid (GABA). Furthermore, it is known that GABA has a ubiquitous inhibitory role in modulating brain function. Most importantly, it is now clear that benzodiazepines share a biochemical property in that all augment the activity of GABA. See Anxiety disorders, Serotonin

The symptoms of depression can include a sense of sadness, hopelessness, despair, and irritability, as well as suicidal thoughts and attempts, which are sometimes successful. In addition, physical symptoms such as loss of appetite, sleep disturbances, and psychomotor agitation are often associated with depression. When depression becomes so pervasive and intense that normal functioning is impaired, antidepressant medication may be indicated. It has been estimated that as much as 6% of the population will require antidepressant medication at some time in their lives.

There are two major groups of antidepressant drugs. Members of the first group are called heterocyclics because of their characteristic chemical structures. Members of the second group, which are less often prescribed, are called monoamine oxidase inhibitors. See Monoamine oxidase

The antidepressants typically require at least several weeks of chronic administration before they become effective in alleviating depression. This contrasts with the anxiolytics, which are effective in reducing anxiety in hours and even minutes. Another difference between these two classes of drugs is that the anxiolytics are more likely to be efficacious: anxiolytics are effective in the vast majority of nonphobic, anxious patients, whereas the antidepressants are effective in only about 65–70% of depressed patients. See Affective disorders

Manic episodes are characterized by hyperactivity, grandiosity, flight of ideas, and belligerence; affected patients appear to be euphoric, have racing thoughts, delusions of grandeur, and poor if not self-destructive judgment. Periods of depression follow these episodes of mania in the majority of patients. The cycles of this bipolar disorder are typically interspersed among periods of normality that are, in most cases, relatively protracted.

Mania can usually be managed by chronic treatment with lithium salts and can be expected to be effective in 70–80% of the individuals treated. Furthermore, the period of depression that typically follows the manic episode can usually be prevented, or at least attenuated, if lithium treatment is maintained after the manic phase has subsided. Any periods of depression that do occur can be managed by antidepressant drugs. Lithium is no longer the only drug used in the management of mania. Carbamazepine, an anticonvulsant that is used in the treatment of epilepsy, is also useful in the treatment of periods of mania.

Schizophrenia is a form of psychosis; it incorporates a broad range of symptoms that can include bizarre delusions, hallucinations, incoherence of thought processes, inappropriate affect, and grossly disorganized movements. It affects 1–2% of the population. The symptoms of schizophrenia can be controlled, in varying degrees, by a large group of drugs called antipsychotics. Symptom management requires chronic medication and can be expected in about 80% or more of the schizophrenics treated. However, management is only partially successful in that normal functioning is not completely restored in most patients.

The antipsychotics have a broad range of side effects among which are disturbances of movement that fall into two general classes. The first class includes an array of symptoms very like those characteristic of Parkinson's disease. The second class of movement disorder is called tardive dyskinesia. Signs of this disturbance typically include involuntary movements that most often affect the tongue and facial and neck muscles but can also include the digits and trunk.

Although different antipsychotic drugs have different kinds and degrees of side effects, all share a single biochemical action: they all attenuate the activity of dopamine, a naturally occurring substance in the brain. The reduction in dopamine activity produced by the antipsychotics directly accounts for their effects on motor behavior. It is to be expected, therefore, that disrupted dopamine activity in this system would produce disturbances of movement. It is less clear, however, whether reduced dopamine function is also a factor in the process by which these drugs control psychotic (including schizophrenic) symptoms. See Schizophrenia