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Pharmacology: Pharmacodynamics: Levofloxacin is the L-isomer of the racemate, ofloxacin, a quinolone antibacterial agent. The mechanism of action of levofloxacin and other quinolones involves inhibition of bacterial topoisomerase II (DNA gyrase) and topoisomerase IV enzymes which are essential for DNA replication, transcription, repair, and recombination.
Pharmacokinetics: Levofloxacin pharmacokinetics are linear and predictable after single and multiple oral/intravenous (IV) dosing regimens. Steady-state conditions are reached within 48 hours after a 500 mg or 750 mg once daily dosage regimen. The oral and IV route of administration may also be considered interchangeable since levofloxacin's plasma concentration profiles are nearly superimposable in the post-peak, distribution-elimination phase.
The mean volume of distribution generally ranges from 74 to 112 L after single and multiple 500 mg or 750 mg doses, indicating widespread distribution into body tissues. Penetration of levofloxacin in skin tissues and in blister fluid is rapid and extensive. It also penetrates well into lung tissues. Protein binding is approximately 24% to 38% and is independent of drug concentration.
Levofloxacin is stereochemically stable in plasma and urine and undergoes limited metabolism in humans with less than 5% of an administered dose recovered in the urine.
Plasma half-life (t1/2) ranges from approximately 6 to 8 hours. The mean apparent total body clearance and renal clearance range from approximately 144 to 226 mL/min and 96 to 142 mL/min, respectively. Renal clearance in excess of the glomerular filtration rate suggests that tubular secretion of levofloxacin occurs in addition to its glomerular filtration.
Microbiology: Antimicrobial Spectrum of Activity: Levofloxacin has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections: See Table 1.
Click on icon to see table/diagram/imageLevofloxacin has been shown to be active in vitro against most strains of the following organisms; however, the clinical significance of these data is unknown: See Table 2.
Click on icon to see table/diagram/imageIt is suggested to carry out susceptibility tests.
