The convulsant interaction between enoxacin (ENX), a new quinolone antibacterial agent (NQ), and felbinac (FLB), a non-steroidal anti-inflammatory drug (NSAID), in vivo was reproduced as the change of GABA-induced current response in Xenopus oocytes injected with mouse brain mRNA. GABA (10 muM) response was inhibited by ENX in a dose-dependent manner, and IC50 of ENX was 96 muM. Moreover, the inhibitory effect of ENX was 80-fold potentiated in the presence of 10 muM FLB. The GABA(A)-antagonistic interaction between these two drugs in vitro was considered a possible mechanism of convulsant reaction after concomitant administration of NQs and NSAIDs in vivo.