A compound of the formula (I) or a tautomeric isoform thereof wherein R1 is selected from the group consisting of halogen, nitro, lower alkyl sulfonyl, cyano, trifluromethyl lower alkyl, lower alkoxy, lower alkoxycarbonyl, carboxy, lower alkyl aminosulfonyl, perfluoro lower alkyl, lower alkylthio, hydroxy lower alkyl, alkoxy lower alkyl, lower alkylthio lower alkyl, lower alkylsulfinyl lower alkyl, lower alkylsulfonyl lower alkyl, lower alkylsulfinyl, lower alkanoyl, aroyl, aryl, aryloxy and R2 is selected from the group consisting of hydrogen, alkyl, alkoxy, alkylthio, and alkylcarbonyl, and their non-toxic, pharmaceutically acceptable base addition salts or pro-drugs thereof. The compounds of the invention are useful in the treatment of nervous system diseases and disorders, which are responsive to modulation of the GABA
