mainly by renal excretion. However, 4-8% of an ofloxacin dose is excreted in the feces. This would indicate a small degree of biliary excretion, as well. Plasma elimination half-life is around 4 to 5 hours in patients and 6.4 to 7.4 hours in elderly patients. Ofloxacin is a racemic mixture, which consists of 50% levofloxacin (the biologically active component) and 50% of its “mirror image” or enantiomer dextrofloxacin. "After multiple-dose administration of 200 mg and 300 mg doses, peak serum levels of 2.2 and 3.6 μg/ml, respectively, are predicted at steady-state. In vitro, approximately 32% of the drug in plasma is protein bound. Floxin is widely distributed to body tissues. Ofloxacin has been detected in blister fluid, cervix, lung tissue, ovary, prostatic fluid, prostatic tissue, skin, and sputum. Pyridobenzoxazine ring appears to decrease the extent of parent compound metabolism. Less than 5% is eliminated by the kidneys as desmethyl or N-oxide metabolites; 4% to 8% by feces." A number of the endogenous compounds have been reported to be affected by ofloxacin as inhibitors, alteraters, and depletors. See the latest package insert for ofloxacin for additional details. Mode of action Ofloxacin is a broad-spectrum antibiotic that is active against both Gram-positive and Gram-negative bacteria. It functions by inhibiting two bacterial type II topoisomerases, DNA gyrase and topoisomerase IV. Topoisomerase IV is an enzyme necessary to separate (mostly in prokaryotes, in bacteria in particular) replicated DNA, thereby inhibiting bacterial cell division. History Ofloxacin is a second-generation fluoroquinolone, being a broader-spectrum analog of norfloxacin, and was synthesized and developed by scientists at Daiichi Seiyaku. It was first approved for marketing in Japan in 1985, for oral administration, and Daiichi marketed it there under the brand name Tarvid. Daiichi, working with Johnson & Johnson, obtained FDA approval in December 1990, under the brand name Floxin, labelled for use in adults with lower respiratory tract infections, skin and skin structure infections, urinary tract infections, prostatitis, and sexually transmitted diseases. By 1991, it was also marketed as Tarvid by Hoechst in the UK, Germany, Belgium, and Portugal; as Oflocet in France, Portugal, Tunisia, and several African countries by Roussel-Uclaf, as Oflocin by Glaxo in Italy, and as Flobacin by Sigma-Tau in Italy. The market for ofloxacin was seen as difficult from its launch; it was approved as a "1C" drug, a new molecular entity with little or no therapeutic gain over existing therapies, and ciprofloxacin, which