Levofloxacin

In patients receiving systemically administered quinolones, including levofloxacin, serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported, some following the first dose. Some reactions were accompanied by cardiovascular collapse, loss of consciousness, angioedema, (including laryngeal, pharyngeal or facial edema), airway obstruction, dyspnea, urticaria and itching. If an allergic reaction to levofloxacin occurs, discontinue the drug. Serious acute hypersensitivity reactions may require immediate emergency treatment. Oxygen and airway management should be administered as clinically indicated.

As with other anti-infectives, prolonged use may result in overgrowth of non-susceptible organisms, including fungi. If superinfection occurs, discontinue use and institute alternative therapy. Whenever clinical judgment dictates, the patient should be examined with the aid of magnification, such as slit-lamp biomicroscopy, and where appropriate, fluorescein staining.

Patients should be advised not to wear contact lenses if they have signs and symptoms of corneal ulcer.

Pregnancy Category C

Teratogenic Effects: Levofloxacin at oral doses of 810 mg/kg/day in rats caused decreased fetal body weight and increased fetal mortality. No teratogenic effect was observed when rabbits were dosed orally as high as 50 mg/kg/day, at which systemic exposure was estimated to be 250 times that observed at the maximum recommended human ophthalmic dose, or when dosed intravenously as high as 25 mg/kg/day, at which systemic exposure was estimated to be 120 times that observed at the maximum recommended human ophthalmic dose.

There are, however, no adequate and well-controlled studies in pregnant women. Levofloxacin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Levofloxacin has not been measured in human milk. Based on data from ofloxacin, it can be presumed that levofloxacin is excreted in human milk. Caution should be exercised when levofloxacin is administered to a nursing mother.

Safety and effectiveness in children below the age of six years have not been established. Oral administration of systemic quinolones has been shown to cause arthropathy in immature animals. There is no evidence that the ophthalmic administration of levofloxacin has any effect on weight bearing joints.

No overall differences in safety or effectiveness have been observed between elderly and other adult patients.

Levofloxacin is a member of the fluoroquinolone class of anti-microbial drug (See  12.4 Microbiology).

Levofloxacin concentration in plasma was measured in 14 healthy adult volunteers during a 16-day course of treatment with levofloxacin ophthalmic solution. The dosing schedule was 1 to 2 drops per eye once in the morning on Days 1 and 16; 1 to 2 drops per eye every two hours Days 2 through 8; and 1 to 2 drops per eye every four hours Days 9 through 15. The mean levofloxacin concentration in plasma 1 hour post dose ranged from 3.13 ng/mL on Day 1 to 10.4 ng/mL on Day 16.

Maximum mean levofloxacin concentrations increased from 3.22 ng/mL on Day 1 to 10.9 ng/mL on Day 16, which is more than 400 times lower than those reported after standard oral doses of levofloxacin.

Levofloxacin concentration in tears was measured in 100 healthy adult volunteers at various time points following instillation of 2 drops of levofloxacin ophthalmic solution. Mean tear concentration measured 15 minutes after instillation was 757 mcg/mL.

Levofloxacin is the L-isomer of the racemate, ofloxacin, a quinolone antimicrobial agent. The antibacterial activity of ofloxacin resides primarily in the L-isomer. The mechanism of action of levofloxacin and other fluoroquinolone antimicrobials involves the inhibition of bacterial topoisomerase IV and DNA gyrase (both of which are type II topoisomerases), enzymes required for DNA replication, transcription, repair, and recombination.

Levofloxacin has in vitro activity against a wide range of Gram-negative and Gram-positive microorganisms and is often bactericidal at concentrations equal to or slightly greater than inhibitory concentrations.

Fluoroquinolones, including levofloxacin, differ in chemical structure and mode of action from ß-lactam antibiotics and aminoglycosides, and therefore may be active against bacteria resistant to ß-lactam antibiotics and aminoglycosides. Additionally, ß-lactam antibiotics and aminoglycosides may be active against bacteria resistant to levofloxacin. Resistance to levofloxacin due to spontaneous mutation in vitro is a rare occurrence (range: 10^{- 9} to 10^{- 10}).

Levofloxacin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.

Aerobic gram-positive microorganisms:

Corynebacterium species*

Staphylococcus aureus

Staphylococcus epidermidis

Streptococcus pneumoniae

Viridans group streptococci*

Aerobic gram-negative microorganisms:

Pseudomonas aeruginosa

Serratia marcescens*

*Efficacy for this organism was studied in fewer than 10 infections.

The following in vitro data are also available, but their clinical significance in ophthalmic infections is unknown.  The safety and effectiveness of levofloxacin in treating ophthalmological infections due to these microorganisms have not been established in adequate and well controlled trials.

These organisms are considered susceptible when evaluated using systemic breakpoints. However, a correlation between the in vitro systemic breakpoint and ophthalmological efficacy has not been established. The list of organisms is provided as guidance only in assessing the potential treatment of corneal ulcer. Levofloxacin exhibits in vitro minimal inhibitory concentrations (MICs) of 2 mcg/mL or less (systemic susceptible breakpoint) against most (≥ 90%) strains of the following ocular pathogens:

Aerobic gram-positive microorganisms:

Enterococcus faecalis (many strains are only moderately susceptible)

Staphylococcus saprophyticus

Streptococcus agalactiae

Streptococcus pyogenes

Streptococcus (Group C/F)

Streptococcus (Group G)

Aerobic gram-negative microorganisms:

Acinetobacter baumannii

Acinetobacter lwoffii

Citrobacter koseri

Citrobacter freundii

Enterobacter aerogenes

Enterobacter cloacae

Escherichia coli

Haemophilus influenzae

Haemophilus parainfluenzae

Klebsiella oxytoca

Klebsiella pneumonia

Legionella pneumophila

Moraxella catarrhalis

Morganella morganii

Neisseria gonorrhoeae

Pantoea agglomerans

Proteus mirabilis

Proteus vulgaris

Providencia rettgeri

Providencia stuartii

Pseudomonas fluorescens

In a long term carcinogenicity study in rats, levofloxacin exhibited no carcinogenic or tumorigenic potential following daily dietary administration for 2 years at doses up to 100 mg/kg/day, corresponding to plasma levels that were 245 times maximum clinical exposure, based on C _max.

Levofloxacin was not mutagenic in the following assays: Ames bacterial mutation assay (S. typhimurium and E. coli) CHO/HGPRT forward mutation assay, mouse micronucleus test, mouse dominant lethal test, rat unscheduled DNA synthesis assay, and the in vivo mouse sister chromatid exchange assay. It was positive in the in vitro chromosomal aberration (CHL cell line) and in vitro sister chromatid exchange (CHL/IU cell line) assays. Levofloxacin caused no impairment of fertility or reproduction in rats at oral doses as high as 360 mg/kg/day, at which systemic exposure was estimated to be 2,600 times that at the maximum recommended human ophthalmic dose.

Advise patients to avoid contaminating the applicator tip with material from the eye, finger, or other source.

Advise patients not to wear contact lenses if they have signs and symptoms of corneal ulcer.

Systemically administered quinolones, including levofloxacin, have been associated with hypersensitivity reactions, even following a single dose. Advise patients to discontinue use immediately and contact their physician at the first sign of a rash or allergic reactions.