Pharmacology: Pharmacodynamics: Moxifloxacin is synthetic, broad-spectrum fluoroquinolone antibacterial agent that inhibits DNA gyrase and topoisomerase IV. DNA gyrase is an essential enzyme that is involved in the replication, transcription, and repair of bacterial DNA. Topoiosmerase IV is an enzyme known to play a key role in the partitioning of the chromosomal DNA during bacterial cell division.
Pharmacokinetics: Absorption: Moxifloxacin is well absorbed from the GI tract. Coadministration with a high-fat meal does not affect the absorption of moxifloxacin. Steady state is achieved after ≥3 days with a 400 mg once-daily regimen.
Distribution: The volume of distribution ranges from 1.7 to 2.7 L/kg. Moxifloxacin is widely distributed throughout the body, with tissue concentrations often exceeding plasma concentrations.
Metabolism/Excretion: Moxifloxacin is metabolized via glucuronide and sulfate conjugation. The sulfate conjugate (M1) accounts for ~38% of the dose and is eliminated primarily in the feces. Approximately 14% of an oral dose are converted to a glucuronide conjugate (M2), which is excreted exclusively in the urine. A total of 96% of an oral dose is excreted as either unchanged drug or known metabolites. The mean apparent total body clearance and renal clearance are ~ 12 L/hr and 2.6 L/hr, respectively. (See Table 1.)
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Microbiology: The following organisms are generally susceptible to moxifloxacin in vitro: Gram negative: Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumonia, Moraxella-catarrhalis.
Gram positive: Staphylococcus aureus (methicillin susceptible), Streptococcus anginosus, Streptococcus constellatus, Streptococcus pneumoniae, Enterococcus faecalis.
Atypical bacteria: Mycoplasma pneumonia, Chlamydia pneumoniae.
Moxifloxacin exhibits in vitro minimum inhibitory concentrations (MICs) ≤2 mcg/mL against most (≥90%) strains of the following microorganisms; however, the safety and effectiveness of moxifloxacin in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.
Gram negative: Citrobacter freundii, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Proteus mirabilis.
Gram positive: Staphylococcus epidermidis (methicillin susceptible), Streptococci pyogenes, Streptococcus viridans, Streptococcus agalactiae.
Atypical bacteria: Legionella pneumophilia.