Adults

Initial dose is typically 12.5 mg orally once daily, gradually titrated upwards at weekly intervals in 12.5 mg increments, administered in 2-3 divided doses. Maximum dose is usually 100 mg/day (for Huntington's chorea) or 50 mg/day (for tardive dyskinesia).

Elderly

Start with a lower initial dose and titrate slowly, monitoring for adverse effects due to potential decreased metabolic capacity.

Renal_impairment

No specific dose adjustment for mild to moderate renal impairment; use with caution in severe renal impairment as tetrabenazine and its metabolites are primarily eliminated renally. Consult physician.

Onset

Therapeutic effects typically observed within a few weeks of dose titration.

Excretion

Primarily eliminated via the kidneys (urine) as metabolites, with a small portion excreted in feces.

Half life

Parent drug: approximately 5-9 hours. Active metabolites (α-HTBZ, β-HTBZ): approximately 1-3 hours.

Absorption

Rapidly absorbed after oral administration, but undergoes extensive first-pass metabolism.

Metabolism

Extensively metabolized by cytochrome P450 2D6 (CYP2D6) to two major active metabolites, α-dihydrotetrabenazine (α-HTBZ) and β-dihydrotetrabenazine (β-HTBZ).

MAO Inhibitors

Concomitant use is contraindicated due to increased risk of hypertensive crisis and severe adverse reactions. A 14-day washout period is required between stopping MAOIs and initiating tetrabenazine.

CYP2D6 Inhibitors

Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine, quinidine) can significantly increase plasma concentrations of tetrabenazine's active metabolites. Dose reduction of tetrabenazine may be necessary.

QT-Prolonging Drugs

Concurrent use with other drugs known to prolong the QT interval may increase the risk of cardiac arrhythmias. Use with caution.

CNS Depressants (e.g., alcohol, benzodiazepines)

Additive sedative effects may occur. Use with caution.