Tetrabenazine

INTRODUCTION

Indications

Treatment of chorea due to Huntington's disease.

Action

Acts as a reversible inhibitor of the vesicle monoamine transporter type 2 (VMAT-2); which inhibits the reuptake of serotonin, norepinephrine, and dopamine into vesicles in presynaptic neurons. Therapeutic Effects: ↓ chorea due to Huntington's disease.

Adverse Reactions/Side Effects

CNS: anxiety, fatigue, insomnia, depression, sedation/somnolence, cognitive defects, dizziness, headache. Resp: shortness of breath. CV: hypotension, QTc prolongation. GI: nausea, dysphagia. Neuro: akathisia, balance difficulty, dysarthria, parkinsonism, unsteady gait. Misc: NEUROLEPTIC MALIGNANT SYNDROME.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Be alert for signs of neuroleptic malignant syndrome, including hyperthermia, diaphoresis, generalized muscle rigidity, altered mental status, tachycardia, changes in blood pressure (BP), and incontinence. Report these signs to the physician or nursing staff immediately.

• Document the incidence and severity of involuntary movements related to chorea (rapid jerky motions, other dyskinesias) to help document whether this drug is successful in reducing these symptoms. Notify physician of changes in abnormal movements to help find an optimal dose of this drug to control chorea.

• Assess BP periodically and compare to normal values (See Appendix F). Report low BP (hypotension), especially if patient experiences dizziness, fatigue, or other symptoms.

• Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report any rhythm disturbances or symptoms of increased arrhythmias, including palpitations, chest discomfort, shortness of breath, fainting, and fatigue/weakness.

• Assess dizziness, Parkinson-like symptoms, severe restlessness (akathisia), or other motor problems that affect gait, balance, and functional activities. Report balance problems and functional limitations to the physician and nursing staff, and caution the patient and family/caregivers to guard against falls and trauma.

• Monitor anxiety, depression, decreased cognition, and other psychologic problems. Repeated or excessive symptoms may require change in dose or medication.

Interventions

• Implement therapeutic exercises (coordination exercises, gait training) to complement the effects of drug therapy and help achieve optimal function.

• Because of the risk of arrhythmias and abnormal BP responses, use caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (BP, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

• Guard against falls and trauma (hip fractures, head injury, and so forth). Implement fall- prevention strategies (See Appendix E), especially if patient exhibits motor problems (Parkinson symptoms, postural instability, rigidity) combined with drug side effects (dizziness, balance deficits).

Patient/Client-Related Instruction

• Advise patient to avoid alcohol because of the increased risk of sedation and adverse effects.

• Instruct patient to report other troublesome side effects such ...