The present invention relates to a composition of enantiomers of 3,6,77a-tctrahydro-1H- pyrrolo[1,5-a]imidazole-2,5-dione and pharmaceutically acceptable solvates or co-crystals thereof in a certain ratio, a pharmaceutical composition comprising said composition, its use as a medicament and the use of the inventive compositions or pharmaceutical compositions in the treatment and/or prevention of a disease or disorder typically and preferably selected from peripheral sensory neuropathy, preferably peripheral neuropathic pain； seizure； depression； or cognitive impairment.
