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Pharmacology: Levofloxacin is the optical S-(-) isomer of ofloxacin. It has a wide-spectrum antibacterial effect. Levofloxacin is active against Gram-positive and Gram-negative bacteria including anaerobes. Moreover, levofloxacin has shown antibacterial activity against Chlamydia pneumoniae and Mycoplasma pneumoniae. Levofloxacin is often bactericidal at concentrations equal to or slightly greater than inhibitory concentration.
The main mechanism of action of levofloxacin is through the inhibition of DNA gyrase, a type II topoisomerase. It is resulting in inhibition of bacterial DNA replication and transcription.
Levofloxacin is rapidly and essentially completely absorbed after oral administration. Peak plasma concentrations are usually attained one to two hours after oral dosing. The absolute bioavailability of a 500 mg oral dose of levofloxacin is approximately 99%. Food has little effect on the absorption of levofloxacin. The peak and trough plasma concentrations attained following multiple once-daily oral 500 mg regimens were approximately 5.7 and 0.5 μg/mL, respectively. The peak and trough concentration attained following multiple once-daily IV 500-mg regimens were approximately 6.4 and 0.6 μg/mL, respectively, after the 750 mg doses were 12.1 and 1.3 μg/mL, respectively.
Levofloxacin is widely distributed throughout the body in high concentration. Levofloxacin also penetrates well into lung tissue. Lung tissue concentrations were generally 2 to 5 fold higher than plasma concentrations and ranged from approximately 2.4 to 11.3 μg/g over a 24 hour period after a single 500 mg oral dose.
Levofloxacin penetrates rapidly into bronchial mucosa and epithelial lung fluid (ELF) with maximum concentration in bronchial mucosa and epithelial lining fluid after 500 mg per oral were 8.3 μg/g and 10.8 μg/mL, respectively. These were reached approximately one hour after administration. Levofloxacin is metabolised to a very small extent, the metabolites being desmethyl- levofloxacin and levofloxacin N-oxide. These metabolites account for < 5 % of the dose excreted to urine.
Following oral and intravenous administration of levofloxacin, it is eliminated relatively slowly from the plasma (t½ = 6-8 hours). Excretion is primarily by the renal route (> 85 % of the administered dose).
Clearance of levofloxacin is reduced and plasma elimination half-life is prolonged in patients with impaired renal function (creatinine clearance ≤ 80 mL/min), requiring dosage adjustment in such patients to avoid accumulation.
The majority of the drug is not metabolized in the body. About 85% of the administered dose is excreted in urine as an unchanged form.
