What causes tardive dyskinesia

What is Tardive Dyskinesia?

Tardive dyskinesia (TD) is a potentially irreversible, involuntary movement disorder that can develop as a side effect of certain medications. These medications are typically antipsychotics, which are commonly used to treat chronic mental health conditions like schizophrenia, bipolar disorder, and depression. However, TD can also be associated with other drugs, including some anti-nausea medications and certain antidepressants, although this is less common.

The term "tardive" refers to the fact that the disorder often appears late, sometimes months or even years, after a person starts taking the medication, or after a dose increase. "Dyskinesia" refers to abnormal, involuntary movements.

What Causes Tardive Dyskinesia?

The primary cause of tardive dyskinesia is the long-term use of dopamine receptor blocking agents, most notably antipsychotic medications. Antipsychotics work by blocking dopamine receptors in the brain. Dopamine is a neurotransmitter that plays a crucial role in regulating movement, mood, and reward pathways.

While blocking dopamine can be effective in managing symptoms of psychosis, prolonged blockade, particularly of D2 receptors, is believed to lead to changes in the dopamine system. Over time, the brain may become hypersensitive to dopamine, or changes may occur in the number or sensitivity of dopamine receptors. This imbalance is thought to disrupt the normal functioning of the basal ganglia, a part of the brain responsible for controlling voluntary motor movements, leading to the characteristic involuntary movements of TD.

Medications Involved

Antipsychotics: These are the most common culprits. They are divided into two main classes:

• First-generation (typical) antipsychotics: Examples include haloperidol (Haldol), fluphenazine (Prolixin), and chlorpromazine (Thorazine). These older medications are generally considered to have a higher risk of causing TD.
• Second-generation (atypical) antipsychotics: Examples include risperidone (Risperdal), olanzapine (Zyprexa), quetiapine (Seroquel), and aripiprazole (Abilify). While often having a lower risk profile than typical antipsychotics, they can still cause TD, especially with long-term use.

Other Medications:

• Antiemetics (anti-nausea drugs): Certain medications used to treat nausea and vomiting, such as metoclopramide (Reglan), can also block dopamine receptors and carry a risk of TD.
• Other Psychiatric Medications: In rare cases, other drugs that affect neurotransmitters, like some selective serotonin reuptake inhibitors (SSRIs), might be implicated, though the link is less established.

Risk Factors

Several factors can increase an individual's risk of developing tardive dyskinesia:

• Duration of Treatment: The longer a person is on a causative medication, the higher the risk.
• Dosage: Higher doses of these medications are associated with an increased risk.
• Age: Older adults, particularly those over 50, are more susceptible to developing TD.
• Sex: Women appear to be at a higher risk than men.
• Substance Use: Alcohol and illicit drug use can potentially increase the risk.
• Diabetes: Individuals with diabetes may have a higher risk.
• Neurological Conditions: Pre-existing neurological conditions, such as Parkinson's disease or Huntington's disease, can increase vulnerability.
• Genetics: There may be a genetic predisposition in some individuals.

Symptoms of Tardive Dyskinesia

The movements associated with TD are involuntary and can range from mild to severe. They often involve:

• Facial movements: Grimacing, pursing of the lips, puckering, chewing motions, blinking.
• Tongue movements: Protruding the tongue, flicking the tongue, writhing or twisting tongue movements.
• Jaw movements: Clenching, gnashing of teeth, opening and closing the mouth.
• Limb movements: Tapping, foot-shaking, writhing or choreiform (dance-like) movements of the arms and legs.
• Trunk movements: Twisting, rocking, or other involuntary movements of the torso.

These movements can be distressing and significantly impact a person's quality of life, affecting their ability to eat, speak, swallow, and interact socially.

Management and Prevention

The best approach to tardive dyskinesia is prevention. This involves:

• Using the lowest effective dose of causative medication.
• Regularly reassessing the need for the medication.
• Considering alternative treatments with lower TD risk when possible.
• Carefully monitoring patients for any signs of involuntary movements, especially after prolonged treatment.

If TD develops, treatment focuses on managing the symptoms and, if possible, discontinuing or changing the offending medication. However, stopping the medication does not always resolve the TD, and in some cases, the movements may persist or even worsen temporarily after discontinuation.

Newer medications specifically designed to treat TD are available, which can help manage the involuntary movements.