Systemically active anticonvulsant that is 30-100-fold more potent in vivo than the separate enantiomers (S)-3,4-DCPG ((S)-3,4-Dicarboxyphenylglycine ; mGlu 8 -selective agonist) or (R)-3,4,-DCPG ((R)-3,4-Dicarboxyphenylglycine ; AMPA/NMDA antagonist).