Tetrabenazine

Pharmacogenomic Information in the Context of the FDA-Approved Drug Label*

Tetrabenazine is used to treat Huntington's Disease chorea. Its primary metabolites are metabolized mainly by CYP2D6, and people with CYP2D6 poor metabolizer genotypes should be treated with lower doses.

Excerpts from the tetrabenazine drug label:

"DOSAGE AND ADMINISTRATION). Patients should be genotyped for CYP2D6 prior to treatment with daily doses of tetrabenazine
over 50 mg (see WARNINGS - Laboratory Tests). Patients who are PMs should not be given daily doses greater than 50 mg."

"Before patients are given a daily dose of greater than 50 mg, they should be tested for the CYP2D6 gene to determine whether they
are poor metabolizers (PMs) or extensive or intermediate metabolizers (EMs or IMs). When a dose of tetrabenazine is given to PMs,
exposure will be substantially higher (about 3-fold for a-HTBZ and 9-fold for b-HTBZ) than it would be in EMs. The dosage should
therefore be adjusted according to a patient's CYP2D6 metabolizer status by limiting the dose to 50 mg in patients who are CYP2D6
poor metabolizers."

(For the complete drug label text with sections containing pharmacogenetic information highlighted, see the Tetrabenazine drug label PDF.)

The FDA recommends, but does not require, genetic testing prior to initiating treatment with tetrabenazine.