Plasma glutamate and glycine levels in patients with amyotrophic lateral sclerosis: the effect of riluzole treatment

OBJECTIVES: Defective glutamate (glu) metabolism and excitotoxicity have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). Moreover, glycine (gly) has been shown to potentiate excitatory transmission. The "antiglutamatergic" agent riluzole has been shown to prolong survival in ALS. The aim of the study was to investigate a possible effect of riluzole on plasma glu and gly levels, correlating with clinical response to treatment. PATIENTS AND METHODS: Plasma concentrations of glu and gly were measured in 20 healthy volunteers and 22 ALS patients before treatment and after 6 months on riluzole. RESULTS: At baseline, increased plasma glu correlated with spinal onset and male gender whereas gly levels did not differ between patients and controls. No significant change was observed for both amino acids post-treatment, despite a lower rate of disease progression. CONCLUSION: These results suggest that riluzole may affect disease progression without a significant impact on plasma glu and gly levels, possibly indicating different mechanisms of drug action.