Following oral administration to healthy subjects, peak plasma enoxacin concentrations were achieved within 1 to 3 hours. Absolute oral bioavailability of enoxacin is approximately 90%. Maximum plasma concentrations of enoxacin average 0.93 µg/mL and 2.0 µg/mL after single 200 mg and 400 mg doses, respectively. Enoxacin plasma half-life is 3 to 6 hours. Enoxacin is excreted primarily via the kidney. After a single dose, greater than 40% was recovered in urine by 48 hours as unchanged drug. In elderly patients, the mean peak enoxacin plasma concentration was 50% higher than that in young adult volunteers receiving comparable single doses of enoxacin. This appears to correspond to age-associated reduction of renal function in the elderly population. Five metabolites of enoxacin have been identified in human urine and account for 15% to 20% of the administered dose.

Enoxacin diffuses into cervix, fallopian tube, and myometrium at levels approximately 1-2 times those achieved in plasma, and into kidney and prostate at levels approximately 2-4 times those achieved in plasma. Studies have not been conducted to assess the penetration of enoxacin into human cerebrospinal fluid.

Enoxacin is approximately 40% bound to plasma proteins in healthy subjects and is approximately 14% bound to plasma proteins in patients with impaired renal function.

The effect of food on the absorption of enoxacin from the tablet formulation has not been studied.

Some isozymes of the cytochrome P-450 hepatic microsomal enzyme system are inhibited by enoxacin. This inhibition results in significant drug/drug interactions with theophylline and caffeine. Enoxacin interferes with the metabolism of theophylline, resulting in a dose-related decrease in theophylline clearance. Elevated serum theophylline concentrations may increase the risk of theophylline-related adverse reactions. (See PRECAUTIONS : Drug Interactions . )

Clearance of enoxacin is reduced in patients with impaired renal function (creatinine clearance ≤30 mL/min/1.73 m ² ), and dosage adjustment is necessary. (See DOSAGE AND ADMINISTRATION.)

MICROBIOLOGY

Enoxacin is an inhibitor of the bacterial enzyme DNA gyrase and is a bactericidal agent. Enoxacin may be active against pathogens resistant to drugs that act by different mechanisms.

Enoxacin has been shown to be active against most strains of the following organisms both in vitro and in clinical infections: (See INDICATIONS AND USAGE.)

Gram-positive aerobes: Staphylococcus epidermidis, Staphylococcus saprophyticus.

Gram-negative aerobes: Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Neisseria gonorrhoeae, Proteus mirabilis, Pseudomonas aeruginosa.

The following in vitro data are available but their clinical significance is unknown.

In addition, enoxacin exhibits in vitro minimum inhibitory concentrations (MICs) of 2.0 µg/mL or less against most strains of the following organisms; however, the safety and effectiveness of enoxacin in treating clinical infections due to these organisms have not been established in adequate and well-controlled trials.

Gram-negative aerobes: Aeromonas hydrophila, Citrobacter diversus, Citrobacter freundii, Citrobacter koseri, Enterobacter aerogenes, Haemophilus ducreyi, Klebsiella oxytoca, Klebsiella ozaenae, Morganella morganii, Proteus vulgaris, Providencia stuartii, Providencia alcalifaciens, Serratia marcescens, Serratia proteomaculans (formerly S. liquefaciens )

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