Gale Encyclopedia of Mental Disorders - Medication-induced movement disorders
Medication-induced movement disorders
Definition
Medication-induced movement disorder occurs due to treatment with antipsychotic medications. Most medication-induced movement disorders are caused by medications that block the action of dopamine, a neurotransmitter that allows communication between two neurons to take place and that is necessary for coordination of movements of different parts of the body. When the receptor where dopamine is supposed to bind is blocked, certain movement-related side effects occur. All of the medications that block dopamine receptors are called neuroleptics.
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Neuroleptics include both conventional or typical antipsychotic agents, such as chlorpromazine (Thorazine), haloperidol (Haldol), and fluphenazine (Prolixin), as well as the newer, or atypical, antipsychotic agents such as clozapine (Clozaril), risperidone (Risperdal), olanzapine (Zyprexa), and quetiapine (Seroquel). In general, the newer, atypical antipsychotics appear to have a lower likelihood to cause movement disorders than the older, typical medications. Other neuroleptics include certain drugs used in the treatment of physical symptoms such as nausea, and include prochlorperazine, promethazine, and metoclopramide, as well as amoxapine (Asendin), which is marketed as an antidepressant.
There are other medications, however, that do not block dopamine action but still cause movement disorders. They are not referred to as neuroleptics, and they include lithium carbonate , valproic acid and a class of drugs called selective serotonin reuptake inhibitors (SSRIs). The disorder caused by these medications is called medication-induced postural tremor.
All of the disorders caused by neuroleptics, which include antipsychotics and other medications that block dopamine, as well as disorders caused by non-neuroleptic medications, are collectively referred to as medication-induced movement disorders.
Description
Neuroleptics
Medication-induced movement disorders caused by neuroleptics are divided into three time periods. The early-onset type, which usually occurs within the first seven days of treatment with neuroleptics, is known as neuroleptic-induced acute dystonia. Neuroleptic-induced acute dystonia is characterized by abnormal contractions of various muscle groups resulting in spasm and/or twisting of the head, neck, jaw, lips, tongue, and eye muscles as well as abnormal movements and postures of the limbs and the trunk.
The intermediate-onset types of movement disorders associated with the use of neuroleptics usually develop within the first three months of treatment. They are known as neuroleptic-induced Parkinsonism and neurolepticinduced akathisia. Neuroleptic-induced Parkinsonism is associated with difficulty initiating movements. Once movements are initiated, they are very slow. Other characteristics of neuroleptic-induced Parkinsonism are tremor and rigidity in muscles. Neuroleptic-induced akathisia is associated with uncontrollable restlessness that may involve compulsive foot tapping, pacing, and a sense of inner tension.
The late-onset type of neuroleptic-related movement disorder is known as neuroleptic-induced tardive dyskinesia and the onset is usually seen many months to years after starting the neuroleptic treatment. Neurolepticinduced tardive dyskinesia involves grotesque, repetitive, and involuntary movements. They are usually seen in the mouth and face.
A movement disorder that can occur at any time during the course of neuroleptic treatment is known as neuroleptic malignant syndrome. It is a serious condition and is characterized by changes in consciousness, ranging from agitation to coma. The patient may experience high fever, and increases in blood pressure and heart rate, as well as severe muscular rigidity.
Non-neuroleptics
All of the movement disorders mentioned above are related to the use of neuroleptic medications. However, other drugs, such as lithium, valproic acid, isoproterenol, amphetamine, theophylline, as well as a class of drugs known as tricyclic antidepressants, may also cause a movement disorder that is mainly characterized by postural tremor, a rhythmic alteration in movement. Lithium-induced tremor may take the form of twitching in the arms and legs.
Causes and symptoms
Causes
Neuroleptic-induced movement disorders are caused because the actions of dopamine are blocked. Dopamine is a neurotransmitter necessary for coordination of movements of different parts of the body.
Other medications, which are not classified as neuroleptics, block the action of other neurotransmitters as well as dopamine. However, because they essentially block the action of dopamine, they cause similar unwanted effects associated with movements.
Symptoms
Neuroleptic-induced acute dystonia is associated with primarily abnormal postures and muscular spasms. They are usually characterized by abnormal positioning of the head and neck in relation to the body, spasms of the jaw muscles, impaired swallowing, speaking or breathing, thickened or slurred speech due to a slow movement of the tongue, tongue protrusion or tongue dysfunction, eyes deviated up, down, or sideways, and abnormal positioning of the limbs or trunk. Patients experience pain and cramps in the affected muscles. In addition, many patients experiencing dystonia due to the neuroleptic treatment also experience fear and anxiety. This is especially present in patients who are not aware of the possibility of developing dystonia and who mistakenly associate these side effects as part of their mental illness.
