Pharmacokinetics of Ciprofloxacin with Reference to Other Fluorinated Quinolones

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Abstract
The third generation quinolones, ciprofloxacin, enoxacin, fleroxacin, norfloxacin, ofloxacin and pefloxacin are all quickly and quantitatively well (75 - 95% of an oral dose) absorbed upon oral administration. The maximum serum concentrations appear after 1 - 2 hours. The serum and urine concentrations after oral or intravenous ciprofloxacin are direcdy proportional with the doses and follow normal, dose-independent pharmacokinetics. Ciprofloxacin and norfloxacin reach the same serum levels after the same doses. Steady-state levels are indifferent from those after the first dose. In contrast, enoxacin, oflaxacin and pefloxacin do reach somewhat higher levels after chronic administration. Ciprofloxacin is eliminated by the kidneys (active tubular secretion which is blocked by probenecid) (60% after an intravenous administration), by metabolism and by the transintestinal route. Metabolism is minimal (ca. 15-20% for ciprofloxacin and norfloxacin). Transintestinal elimination implies that the drug is eliminated by transport across the intestinal wall without significant biliary elimination (which is less than 1%). Penetration into tissues occurs readily. Concentrations in prostate secretion are high for ciprofloxacin and norfloxacin. Ciprofloxacin reaches high intracellular concentrations; within human neutrophils the levels reach 6 times the concentrations in the surrounding fluid. Concentrations in bile and tissues are in general comparable to those in serum. Cerebrospinal fluid (CSF) concentrations are low when meningi are nomai, but 40-90% of the serum levels when the meninges are inflamed. Because the transintestinal route of elimination compensates for loss of renal elimination, the serum half-life of ciprofloxacvin is raised only to 5 - 10 hours even in total renal failure. Norfloxacin behaves similarly in patients with terminally reduced renal functions, whereas ofloxacin shows increased half-life starting from a creatinine clearance of ca. 30 ml/min; in terminal renal function ofloxacin half-life values are up to 40-50 hours.

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