The initial phase 3 study of edaravone did not show a significant difference in the decline in the
ALS-FRS-R scores in treated patients compared to placebo.. However, a post-hoc analysis and a subsequent phase-3 study revealed that patients in the early stages of ALS with mild symptoms and preserved respiratory function did show a slower progression than did the full study population. The FDA approval of the drug was based on this small study in a population that was followed over a 24 week period, leaving very little time for recordable adverse events to manifest. We hypothesize that although administration of edaravone in the early stages of ALS may be beneficial, there is a more rapid respiratory decline in patients that continue to receive edaravone once respiratory function begins to decline.