Tetrabenazineinteractions

7.1 Strong CYP2D6

Inhibitors In vitro studies indicate that α-HTBZ and β-HTBZ are substrates for CYP2D6. Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine, quinidine) markedly increase exposure to these metabolites. A reduction in tetrabenazine dose may be necessary when adding a strong CYP2D6 inhibitor (e.g., fluoxetine, paroxetine, quinidine) in patients maintained on a stable dose of tetrabenazine. The daily dose of tetrabenazine should not exceed 50 mg per day and the maximum single dose of tetrabenazine should not exceed 25 mg in patients taking strong CYP2D6 inhibitors.

7.2 Reserpine

Reserpine binds irreversibly to VMAT2, and the duration of its effect is several days. Prescribers should wait for chorea to re-emerge before administering tetrabenazine to avoid overdosage and major depletion of serotonin and norepinephrine in the CNS. At least 20 days should elapse after stopping reserpine before starting tetrabenazine. Tetrabenazine and reserpine should not be used concomitantly.

7.3 Monoamine

Oxidase Inhibitors (MAOIs) Tetrabenazine is contraindicated in patients taking MAOIs. Tetrabenazine should not be used in combination with an MAOI, or within a minimum of 14 days of discontinuing therapy with an MAOI.

7.4 Alcohol or

Other Sedating Drugs Concomitant use of alcohol or other sedating drugs may have additive effects and worsen sedation and somnolence.

7.5 Drugs That

Cause QTc Prolongation Tetrabenazine causes a small prolongation of QTc (about 8 msec), concomitant use with other drugs that are known to cause QTc prolongation should be avoided, these including antipsychotic medications (e.g., chlorpromazine, haloperidol, thioridazine, ziprasidone), antibiotics (e.g., moxifloxacin), Class 1A (e.g., quinidine, procainamide) and Class III (e.g., amiodarone, sotalol) antiarrhythmic medications or any other medications known to prolong the QTc interval. Tetrabenazine should be avoided in patients with congenital long QT syndrome and in patients with a history of cardiac arrhythmias. Certain conditions may increase the risk for torsade de pointes or sudden death such as bradycardia; hypokalemia or hypomagnesemia; concomitant use of other drugs that prolong the QTc interval; and presence of congenital prolongation of the QT interval.

7.6 Neuroleptic

Drugs The risk for Parkinsonism, NMS, and akathisia may be increased by concomitant use of tetrabenazine and dopamine antagonists or antipsychotics (e.g., chlorpromazine, haloperidol, olanzapine, risperidone, thioridazine, ziprasidone).

7.7 Concomitant

Deutetrabenazine or Valbenazine Tetrabenazine is contraindicated in patients currently taking deutetrabenazine or valbenazine.