Mechanism of Action

Moxifloxacin is a member of the fluoroquinolone class of anti-infective drugs.

Pharmacokinetics

Moxifloxacin steady-state plasma pharmacokinetics were evaluated in healthy adult male and female subjects who were administered multiple, bilateral, topical ocular doses of MOXEZA™ solution two times daily for four days with a final dose on day 5. The average steady-state AUC0-12 was 8.17 ± 5.31 ng•h/mL. Moxifloxacin Cmax following twice-daily bilateral ophthalmic administration of moxifloxacin AF 0.5% for 5 days is approximately 0.02% of that achieved with the oral formulation of moxifloxacin hydrochloride (Cmax following oral dosing of 400 mg AVELOX*, 4.5 ± 0.5 mcg/mL).

Microbiology

The antibacterial action of moxifloxacin results from inhibition of the topoisomerase II (DNA gyrase) and topoisomerase IV. DNA gyrase is an essential enzyme that is involved in the replication, transcription and repair of bacterial DNA. Topoisomerase IV is an enzyme known to play a key role in the partitioning of the chromosomal DNA during bacterial cell division.

The mechanism of action for quinolones, including moxifloxacin, is different from that of macrolides, aminoglycosides, or tetracyclines. Therefore, moxifloxacin may be active against pathogens that are resistant to these antibiotics and these antibiotics may be active against pathogens that are resistant to moxifloxacin. There is no cross-resistance between moxifloxacin and the aforementioned classes of antibiotics. Cross-resistance has been observed between systemic moxifloxacin and some other quinolones.

In vitro resistance to moxifloxacin develops via multiple-step mutations. Resistance to moxifloxacin occurs in vitro at a general frequency of between 1.8 x 10^-9 to < 1x10^-11 for Gram-positive bacteria.

Moxifloxacin 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:

Aerococcus viridans*
Corynebacterium macginleyi*
Enterococcus faecalis*
Micrococcus luteus*
Staphylococcus arlettae*
Staphylococcus aureus
Staphylococcus capitis
Staphylococcus epidermidis
Staphylococcus haemolyticus
Staphylococcus hominis
Staphylococcus saprophyticus*
Staphylococcus warneri*
Streptococcus mitis*
Streptococcus pneumoniae
Streptococcus parasanguinis*
Escherichia coli*
Haemophilus influenzae
Klebsiella pneumoniae*
Propionibacterium acnes
Chlamydia trachomatis*

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

The following in vitro data are available, but their clinical significance in ophthalmic infections is unknown. The safety and effectiveness of MOXEZA™ solution in treating ophthalmic infections due to these organisms have not been established in adequate and well-controlled trials.

Moxifloxacin has been shown to be active in vitro against most strains of the microorganisms listed below. These organisms are considered susceptible when evaluated using systemic breakpoints; however, a correlation between the in vitro systemic breakpoint and ophthalmologic efficacy has not been established. The list of organisms is provided as guidance only in assessing the potential treatment of conjunctival infections. Moxifloxacin 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

Staphylococcus caprae
Staphylococcus cohnii
Staphylococcus lugdunensis
Staphylococcus pasteuri
Streptococcus agalactiae
Streptococcus milleri group
Streptococcus oralis
Streptococcus pyogenes
Streptococcus salivarius
Streptococcus sanguis

Aerobic Gram-negative microorganisms

Acinetobacter baumannii
Acinetobacter calcoaceticus
Acinetobacter junii
Enterobacter aerogenes
Enterobacter cloacae
Haemophilus parainfluenzae
Klebsiella oxytoca
Moraxella catarrhalis
Moraxella osloensis
Morganella morganii
Neisseria gonorrhoeae
Neisseria meningitidis
Pantoea agglomerans
Proteus vulgaris
Pseudomonas stutzeri
Serratia liquefaciens
Serratia marcescens
Stenotrophomonas maltophilia

Anaerobic microorganisms

Clostridium perfringens
Peptostreptococcus anaerobius
Peptostreptococcus magnus
Peptostreptococcus micros
Peptostreptococcus prevotii

Other microorganisms

Mycobacterium tuberculosis
Mycobacterium avium
Mycobacterium kansasii
Mycobacterium marinum

Clinical Studies

In one randomized, double-masked, multicenter, vehicle-controlled clinical trial in which patients with bacterial conjunctivitis were dosed with MOXEZA™ solution 2 times a day, MOXEZA™ was superior to its vehicle for both clinical and microbiological outcomes. Clinical cure achieved on Day 4 was 63% (265/424) in MOXEZA™ treated patients, versus 51% (214/423) in vehicle treated patients. Microbiologic success (eradication of baseline pathogens) was achieved on Day 4 in 75% (316/424) of MOXEZA™ treated patients versus 56% (237/423) of vehicle treated patients. Microbiologic eradication does not always correlate with clinical outcome in anti-infective trials.

Last reviewed on RxList: 10/1/2012
This monograph has been modified to include the generic and brand name in many instances.