OBJECTIVES: To determine whether chronic treatment with coenzyme Q10 or remacemide hydrochloride slows the functional decline of early Huntington's disease (HD).

METHODS: The authors conducted a multicenter, parallel group, double-blind, 2 x 2 factorial, randomized clinical trial. Research participants with early HD (n = 347) were randomized to receive coenzyme Q10 300 mg twice daily, remacemide hydrochloride 200 mg three times daily, both, or neither treatment, and were evaluated every 4 to 5 months for a total of 30 months on assigned treatment. The prespecified primary measure of efficacy was the change in total functional capacity (TFC) between baseline and 30 months. Safety measures included the frequency of clinical adverse events.

RESULTS: Neither intervention significantly altered the decline in TFC. Patients treated with coenzyme Q10 showed a trend toward slowing in TFC decline (13%) over 30 months (2.40- versus 2.74-point decline, p = 0.15), as well as beneficial trends in some secondary measures. There was increased frequency of nausea, vomiting, and dizziness with remacemide and increased frequency of stomach upset with coenzyme Q10.

CONCLUSIONS: Neither remacemide nor coenzyme Q10, at the dosages studied, produced significant slowing in functional decline in early HD.