Double-Blind Crossover Study with Levorotatory form of Hydroxytryptophan in Patients with Degenerative Cerebellar Diseases

To determine whether treatment with the levorotatory form of hydroxytryptophan (l-5-hydroxytryptophan), a controversial experimental drug, can improve the conditions of patients with ataxia. A double-blind crossover study with the levorotatory form of hydroxytryptophan was performed in 39 patients with degenerative cerebellar diseases. Patients were selected from an ongoing prospective follow-up study at two university hospitals. We studied 19 patients with Friedreich's ataxia, 13 with cerebellar atrophy, and seven with olivopontocerebellar atrophy. The levorotatory form of hydroxytryptophan was given orally in a dose of 1000 mg/d. Each treatment phase, with the levorotatory form of hydroxytryptophan or the placebo, lasted 10 months, after which the treatment of patients was crossed over to the other phase. Ataxia was documented and quantified by using a clinical score, posturography, and measurement of grip force and the rapid-syllable repetition rate. The levorotatory form of hydroxytryptophan had no significant effect on cerebellar symptoms. Long-term treatment with a high dose of the levorotatory form of hydroxytryptophan does not improve the conditions of patients with ataxia.