The effect of the levorotatory form of 5-hydroxytryptophan (approx 1 gm/day/orally) on cerebellar symptoms in 26 patients with Friedreich’s ataxia was evaluated in a double-blind drug-placebo study by the Ataxia Research Center, Hopital Neurologique, Lyon and 11 other research hospitals in France. Of 19 completing the study, 11 were treated with 5-hydoxytryptophan and 8 with placebo. A significant decrease of the kinetic score and improvement in coordination was observed in the active treatment group after 6 months but not at 4 months, indicating a progressive drug effect. Five subtests demonstrating improvement included finger-nose test, heel-knee, and Archimedes’ spiral. A trend toward acceleration of the speed of speech was also observed. Gastrointestinal symptoms were the main side-effects of treatment. [1]
COMMENT. The effect of 5-hydroxytryptophan was only partial, improving kinetic ataxic symptoms but not the static scores involving posture. In another double-blind crossover study at the Medical University of Lubeck, and other centers in Germany, Wessel K et al reported no significant effect of hydroxytrytophan on cerebellar symptoms in 19 patients with Friedreich’s ataxia [2]. Currier RD, in an editorial, concludes that “the levorotatory form of 5-hydoxytryptophan may have an effect that is minimal, selective, and difficult to detect. The question of clinical usefulness is not settled.”