The present invention relates to compositions comprising S-tofisopam substantially free of R-tofisopam, and methods for treating or preventing convulsions and/or seizures comprising administration of the composition to subjects in need of treatment therefor. Also provided are compositions and methods for treating or preventing convulsions and/or seizures comprising administering S-tofisopam substantially free of R-tofisopam with another anti-convulsant.