Antibacterial activity of ofloxacin and other 4-quinolone derivatives: in-vitro and in-vivo comparison.

Ofloxacin (DL8280, RU43280) is a newly introduced oxazine quinolone derivative with broad and potent antibacterial activity. Ofloxacin showed excellent in-vitro activity against Enterobacteriaceae while most strains of Pseudomonas aeruginosa were inhibited by less than 2 mg/l. The compound was significantly more potent than norfloxacin against Acinetobacter spp. and Staphylococcus spp. Ofloxacin and norfloxacin behaved similarly with respect to inoculum size, effect of urine and serum, bactericidal properties and frequency of spontaneous resistant mutants. Ofloxacin displayed an in-vivo antibacterial activity up to five times greater than that of pefloxacin and norfloxacin, probably due to the conjunction of favourable pharmacokinetics, excellent bacterial susceptibility and good stability towards metabolic degradation.