Tetrabenazine is a prescription medication designed to address specific neurological conditions characterized by involuntary movements. It functions by altering the levels of natural chemicals, known as monoamines, within the brain. This action on dopamine and serotonin helps to reduce excessive and unintentional physical actions. The medication is not a cure for the underlying diseases but serves as a method to manage some of their more disruptive symptoms.
Medical Uses for Tetrabenazine
The primary approved use for tetrabenazine is the treatment of chorea, which involves jerky, unpredictable, and involuntary movements associated with Huntington’s disease. Huntington’s is a progressive genetic disorder that causes the breakdown of nerve cells in the brain, leading to a decline in motor, cognitive, and psychiatric functions.
While its main indication is for Huntington’s-related chorea, tetrabenazine is sometimes prescribed for other conditions involving excess movement. These “off-label” uses can include managing tardive dyskinesia, a condition causing repetitive, involuntary movements often resulting from long-term use of certain psychiatric drugs. It may also be used for controlling the tics associated with Tourette syndrome.
Reported Effectiveness on Movement Control
Clinical evidence indicates that tetrabenazine can effectively reduce the severity of chorea. The medication works by depleting presynaptic dopamine, a neurotransmitter that facilitates movement. This is achieved through its mechanism as a vesicular monoamine transporter 2 (VMAT2) inhibitor, which prevents dopamine from being stored and released by nerve cells. This reduction in available dopamine helps suppress unwanted movements.
The level of improvement can vary considerably among individuals. Some patients report a marked reduction in chorea, leading to better functional ability in daily activities. In long-term studies, a high percentage of patients achieved a significant response in chorea reduction at their optimal dose.
Significant Side Effects and Risks
Treatment with tetrabenazine is associated with several common side effects, which are often related to the dosage and can sometimes be managed by adjusting the amount of medication taken. The most frequently reported effects include:
- Drowsiness or sedation
- Insomnia
- Fatigue
- Anxiety or restlessness (akathisia)
- Gastrointestinal issues like nausea
A more serious concern is the potential for the medication to cause symptoms that mimic Parkinson’s disease, such as tremors, stiffness, and slowed movement. This condition, known as drug-induced parkinsonism, arises because the medication reduces dopamine, the same neurotransmitter deficient in Parkinson’s disease.
The U.S. Food and Drug Administration (FDA) has placed a black box warning on tetrabenazine for the risk of depression and suicidal thoughts. Because the drug’s action of depleting brain chemicals can impact mood regulation, it is not recommended for individuals with a history of depression or suicidality. Patients and their families must watch closely for any changes in mood or behavior and report them to a healthcare provider.
Managing Treatment and Dosing
Initiating treatment with tetrabenazine requires a careful and individualized approach to dosing. Physicians start patients on a low dose and gradually increase it over several weeks in a process called titration. This allows the doctor to find the lowest effective dose that provides a meaningful reduction in chorea while minimizing adverse effects. The final dosage can vary widely among patients.
The titration phase necessitates close communication between the patient and their healthcare provider to track effectiveness and manage side effects. Dose adjustments are common and may be required to balance the benefits of movement control against challenges like drowsiness or mood changes. As the underlying disease progresses or as tolerance for the medication changes, the dosage may need to be modified.