Incidence of depressed mood in individuals taking an antidepressant and tetrabenazine
At baseline, 27 (56%) of the 48 participants randomized to tetrabenazine who completed the trial were taking an antidepressant. The incidence of depressed mood as an adverse event did not differ between those taking (15%) and not taking (5%) an antidepressant (p=0.37), and the proportion of individuals experiencing a substantial worsening in their mood scores did not differ (7% v. 10%; p=1.00). The results were similar when examining all 54 participants randomized to tetrabenazine (Table 1).
Table 1. Depression in participants on and not on antidepressants at baseline
* As measured by the Unified Huntington's Disease Rating Scale
** P-values were obtained using Fisher’s exact tests
Effect of tetrabenazine on individuals with advanced HD
At baseline, based on chorea scores, 14 of the 54 (26%) participants enrolled had advanced HD, and based on function, 22 (41%) had advanced HD. The decline in chorea was 8.1 units for those with a baseline chorea of 19 or greater compared to 4.3 units for those with a baseline chorea of between 10 and 18 (p<0.01). However, the relative rates of decline in chorea between the two groups did not differ (p=0.62). Results for participants who completed the study were similar.
Among the 48 participants completing the study, the 12-week clinical global improvement scores between the two groups did not differ (p=0.95). The proportion of individuals with at least one adverse event among those with advanced HD was 75% compared to 80% for those without advanced HD. The numbers of adverse events reported did not differ between the two groups (p=0.18). Results were similar when the entire tetrabenazine cohort was included in the analyses.
Defining advanced HD by total functional capacity scores generated similar results (Table 2).
Table 2. Efficacy and safety of tetrabenazine by baseline disease severity
SD = standard deviation
* P-values were obtained from adjusted multiple regression models.
** P-values were obtained using Cochran-Armitage trend tests.