Levofloxacin is a broad-spectrum third-generation fluoroquinolone and one of the isomers of ofloxacin, specificlaly the optical S-(-) isomer. It is a DNA gyrase inhibitor shown to inhibit topoisomerase IV. Levofloxacin was patented in 1985 and is one of the later generation fluoroquinolones referred to as 'respiratory quinolones'. Levofloxacin is insoluble in aqueous solution.