Now that tetrabenazine is available in the United States, many people with HD are taking a look at the drug and wondering if they should try it to reduce their chorea. A new study by Italian researchers analyzed the long term effects of taking TBZ in HD patients who were seen over time at a movement clinic. Sixty-eight patients were included in the retrospective study; they averaged 34 months of treatment.
The researchers point out that the doctors started by prescribing low doses of the drug, given two or three times a day and titrating upwards. This is important to balance benefit with side effects.
The study is a good complement to the double blind placebo controlled studies that were done prior to the FDA approval of TBZ and that the Lighthouse has covered. This study follows what happens with patients over time as they work to manage their condition with their doctors -- they had side effects, their doses were adjusted, and they were prescribed other medications as well. Seven percent of the patients did not benefit from TBZ and it was discontinued. Half of the patients reported at least one side effect and two of them decided to discontinue the drug. Chorea was reduced for the remaining patients, but the magnitude of the benefit was reduced somewhat over time despite increases in dosage.
To enhance the knowledge on the long-term efficacy and safety of tetrabenazine (TBZ) in managing chorea.
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.
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.
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.