Interaction of the new quinolone antibacterial agent levofloxacin with fenbufen in mice.

The interaction of (-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1- piperazinyl)-7-oxo-7H-pyrido[1,2,3-de] [1,4]benzoxazine-6-carboxylic acid hemihydrate (levofloxacin, DR-3355, CAS 100986-85-4) with fenbufen, a nonsteroidal anti-inflammatory agent, in mice was assessed by convulsive seizure and subsequent death in comparison with that of other new quinolones such as DR-3354 (the R-(+)-isomer of ofloxacin), ofloxacin, norfloxacin, enoxacin and ciprofloxacin. Although treatment with each quinolone or fenbufen alone at a dosage level tested in mice showed no changes, coadministration of a large dose of all quinolones and fenbufen caused convulsant death. When compared with the severity of this interaction, it was in the order of enoxacin greater than norfloxacin greater than ciprofloxacin greater than DR-3354 greater than ofloxacin greater than or equal to DR-3355 under these experimental conditions.