The long-term effect of tetrabenazine in the management of Huntington disease.

Objectives: To enhance the knowledge on the long-term efficacy and safety of tetrabenazine (TBZ) in managing chorea.

Methods: We analyzed 68 Huntington disease patients (mean disease duration, 55.8 +/- 34.7 months) who had been treated with TBZ for a mean period of 34.4 +/- 25.2 months (median, 34 months; mode, 48 months; range, 3-104 months). We measured the variation from pretreatment of the motor score of Unified Huntington's Disease Rating Scale at the first follow-up visit and at the latest.

Results: Mean Unified Huntington's Disease Rating Scale-chorea underscore at the time of the pretreatment visit was 10.4 +/- 4.1 (range, 0-28). At the first follow-up, 9.7 +/- 7.8 months after the prescription of TBZ (mean dose, 35.3 +/- 14.7 mg), mean score of chorea was 8.2 +/- 4.1 (-21% compared with baseline), whereas at the latest follow-up visit (mean dose, 57.5 +/- 14.7 mg), it was 9.5 +/- 5.0 (9%). During the follow-up, the clinical benefit persisted, but the magnitude was reduced despite a progressive increase of the doses (up to 60%). Motor improvement was not influenced by sex, or doses or duration of therapy; age at onset was the only predictor of a good outcome. Five patients (7%) did not gain any improvement, and TBZ was discontinued. There were 2 withdrawals because of side effects; 34 patients reported at least 1 side effect.

Conclusions: Tetrabenazine was well tolerated and produced long-term improvement of motor symptoms in Huntington disease patients, although a slight reduction of benefit occurred during the course of treatment.