Medications can sometimes cause unintended side effects, including involuntary or jerky movements. These drug-induced movements are abnormal physical reactions that develop after taking certain prescribed medications. Understanding these potential side effects and the medications associated with them is important. This article explores the different forms of these movements and the pharmaceutical agents that may cause them.
Types of Involuntary Movements
Involuntary movements caused by medication can manifest in several distinct ways. Tardive Dyskinesia is characterized by repetitive, uncontrolled movements. These often affect the face, appearing as grimacing, lip smacking, tongue protrusion, or chewing motions, but can also involve the limbs and trunk.
Dystonia involves sustained or repetitive muscle contractions. This can lead to twisting movements or abnormal, fixed postures of various body parts, including the face, neck, trunk, and limbs. Akathisia presents as a feeling of inner restlessness and an uncontrollable urge to move, often leading to pacing, fidgeting, or constantly shifting position. Individuals with akathisia might describe a sensation of “wanting to jump out of their skin”.
Myoclonus refers to sudden, brief, shock-like jerks of a muscle or a group of muscles. These jerks can be focal, affecting a specific area, or generalized across the body. Tremors are rhythmic, oscillating movements of a body part, such as shaky hands or a quivering voice.
Medications That Can Cause Them
A range of medications can cause involuntary movements, with some drug classes more commonly implicated than others. Antipsychotics are a primary group, particularly first-generation (typical) antipsychotics like haloperidol and chlorpromazine, which have a higher likelihood of causing conditions such as tardive dyskinesia and acute dystonia. Second-generation (atypical) antipsychotics, including risperidone and olanzapine, can also induce these movements, though generally less frequently. These medications are primarily used for psychiatric conditions like schizophrenia and bipolar disorder.
Antiemetics, prescribed to treat nausea and vomiting, are another notable class. Metoclopramide and prochlorperazine, for instance, are strongly linked to tardive dyskinesia and acute dystonic reactions. The risk can be higher with prolonged use.
Antidepressants, including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), can also contribute to involuntary movements. These may cause tremors, akathisia, or myoclonus. In some cases, antidepressants can contribute to serotonin syndrome, which can include myoclonus and tremors.
Stimulants, often used for conditions like ADHD (e.g., methylphenidate and amphetamines), have been known to cause tremors or tics. Mood stabilizers, like lithium, commonly cause tremors. Additionally, some antiepileptic drugs, such as valproic acid and phenytoin, can lead to tremors or dyskinesia. The likelihood of developing these movements varies depending on the specific medication, its dosage, duration of use, and individual patient susceptibility.
How These Movements Develop
The development of drug-induced jerky movements often involves the interplay of neurotransmitters in the brain, particularly those regulating movement. Many medications, especially antipsychotics and antiemetics, primarily exert their effects by blocking dopamine receptors. Dopamine is a chemical messenger that plays a significant role in controlling movement, and disrupting its balance in areas like the basal ganglia can lead to abnormal movements. This dopamine receptor blockade is a key mechanism behind conditions like tardive dyskinesia and acute dystonia.
Some antidepressants can influence serotonin levels in the brain. An imbalance or excess of serotonin, such as in serotonin syndrome, can manifest as myoclonus or tremors.
Other neurotransmitters, such as acetylcholine and GABA, also play roles in movement regulation, and some drugs can indirectly affect their balance. For instance, an imbalance between dopamine and acetylcholine in certain brain pathways is thought to contribute to dystonia. The common thread is the medication’s influence on the brain’s chemical communication systems.
When to Seek Medical Advice
If new or worsening jerky movements develop after starting or changing a medication, consult a healthcare professional promptly. A doctor will assess the movements, review your medication history, and rule out other potential causes.
Never stop prescribed medication without first consulting your doctor. Abruptly discontinuing certain drugs can be dangerous or worsen the underlying medical condition.
Management strategies may involve adjusting the medication dosage, switching to an alternative medication less likely to cause such side effects, or prescribing additional medications specifically to manage the involuntary movements. For conditions like tardive dyskinesia, specific medications like valbenazine and deutetrabenazine are approved treatments. Some drug-induced movements may resolve with medication adjustments, but others, particularly tardive dyskinesia, can be persistent even after the offending medication is stopped.