Dose-ranging study of riluzole in amyotrophic lateral sclerosis. Amyotrophic Lateral Sclerosis/Riluzole Study Group...

Amyotrophic lateral sclerosis (ALS) is a progressive disease with no effective treatment. In an initial study, riluzole decreased mortality and slowed muscle-strength deterioration in ALS patients. We have carried out a double-blind, placebo-controlled, multicentre study to confirm those findings and to assess drug efficacy at different doses.

959 patients with clinically probable or definite ALS of less than 5 years' duration were randomly assigned treatment with placebo or 50 mg, 100 mg, or 200 mg riluzole daily; randomisation was stratified by centre and site of disease onset (bulbar or limb). The primary outcome was survival without a tracheostomy. Secondary outcomes were rates of change in functional measures (muscle strength, functional status, respiratory function, patient's assessments of fasciculation, cramps, stiffness, and tiredness). The primary analysis was the comparison of the 100 mg dose with placebo by intention-to-treat. Drug-effect on survival was assessed before (log-rank test) and after adjustment for known prognostic factors (Cox's model).

At the end of the study, after median follow-up of 18 months, 122 (50.4%) placebo-treated patients and 134 (56.8%) of those who received 100 mg/day riluzole were alive without tracheostomy (unadjusted risk 0.79, p = 0.076; adjusted risk 0.65, p = 0.002). In the groups receiving 50 mg and 200 mg riluzole daily, 131 (55.3%) and 141 (57.8%) patients were alive without tracheostomy (relative to placebo 50 mg adjusted risk 0.76, p = 0.04; 200 mg 0.61, p = 0.0004). There was a significant inverse dose response in risk of death. No functional scale discriminated between the treatment groups. The most common adverse reactions were asthenia, dizziness, gastrointestinal disorders, and rises in liver enzyme activities; they were commonest with the 200 mg dose.

Overall, efficacy and safety results suggest that the 100 mg dose of riluzole has the best benefit-to-risk ratio. This study confirms that riluzole is well tolerated and lengthens survival of patients with ALS.