An open label trial suggested that valproic acid (VPA) improved strength in adults with spinal muscular atrophy (SMA). Herein, the authors report a 12 month, double blind, crossover study of VPA in 33 ambulatory SMA adults aged 20-55 years. After baseline assessments subjects were randomised to receive VPA (10-20 mg/kg/daily) or placebo. At 6 months, patients were switched to the other group. Assessments were performed at 3, 6, and 12 months. The primary outcome was the 6-month change in maximum voluntary isometric contraction testing with pulmonary, electrophysiologic, and functional secondary outcomes. Thirty subjects completed the study. VPA was well tolerated, and compliance was good. There was no change in primary or secondary outcomes at 6 or 12 months. VPA did not improve strength or function in SMA adults. The outcomes used are feasible and reliable and can be employed in future trials in SMA adults.
