Moxifloxacin

• Community-Acquired Pneumonia
• Acute Bacterial Sinusitis
• Skin and Soft Tissue Infections
• Intra-abdominal Infections

Moxifloxacin is a fourth-generation fluoroquinolone antibiotic with broad-spectrum activity against gram-positive, gram-negative, and atypical bacteria. It is commonly used for respiratory tract infections, skin infections, and intra-abdominal infections, offering excellent tissue penetration and once-daily dosing convenience.

Mechanism of Action

Moxifloxacin exerts its bactericidal effects by inhibiting two essential bacterial enzymes:

• DNA gyrase (topoisomerase II): Required for DNA replication, transcription, repair, and recombination
• Topoisomerase IV: Essential for chromosome segregation during bacterial cell division

By inhibiting these enzymes, moxifloxacin prevents bacterial DNA synthesis and leads to cell death. Its 8-methoxy group provides enhanced activity against gram-positive organisms and anaerobes compared to earlier fluoroquinolones, making it particularly effective for respiratory pathogens.

Available Formulations

• Oral tablets: 400 mg film-coated tablets
• IV solution: 400 mg/250 mL for intravenous infusion
• Ophthalmic solution: 0.5% (for bacterial conjunctivitis treatment)

Oral and IV doses are bioequivalent, allowing easy conversion between routes without dose adjustment. This provides flexibility in transitioning hospitalized patients to outpatient oral therapy.

Medical Uses

FDA-Approved Indications:

• Community-acquired pneumonia (CAP) including multidrug-resistant Streptococcus pneumoniae
• Acute bacterial sinusitis
• Acute bacterial exacerbation of chronic bronchitis
• Complicated and uncomplicated skin and skin structure infections
• Complicated intra-abdominal infections (in combination with metronidazole or alone)
• Plague (Yersinia pestis) - prophylaxis and treatment
• Bacterial conjunctivitis (ophthalmic formulation)

Dosing Guidelines

Adults:

• Most infections: 400 mg once daily orally or IV
• Duration: 5-21 days depending on infection type
• Community-acquired pneumonia: 7-14 days
• Acute bacterial sinusitis: 10 days
• Complicated intra-abdominal infections: 5-14 days
• Plague: 10-14 days

No dose adjustment is typically needed for renal or mild-to-moderate hepatic impairment due to balanced elimination.

Important Safety Information

Black Box Warnings:

• Disabling and potentially irreversible adverse reactions affecting tendons, muscles, joints, nerves, and central nervous system
• Exacerbation of myasthenia gravis symptoms
• Reserved for conditions without satisfactory alternative treatment options for certain infections

Contraindications:

• Known hypersensitivity to moxifloxacin or any fluoroquinolone
• Myasthenia gravis (may exacerbate muscle weakness)

Serious Warnings and Precautions:

• QT prolongation: Avoid in patients with known QT prolongation, hypokalemia, or those taking Class IA or III antiarrhythmics
• Tendinitis and tendon rupture risk: Increased with age >60, corticosteroid use, and organ transplantation
• Peripheral neuropathy: Discontinue immediately if symptoms develop
• CNS effects: May cause seizures, increased intracranial pressure, confusion, and toxic psychosis
• Clostridium difficile-associated diarrhea: Monitor for colitis symptoms
• Blood glucose disturbances: Hypoglycemia and hyperglycemia reported

Drug Interactions

• QT-prolonging drugs: Additive arrhythmia risk; avoid concurrent use with antiarrhythmics, antipsychotics, tricyclic antidepressants
• Antacids, iron, zinc, multivitamins: Chelate with moxifloxacin; administer moxifloxacin 4 hours before or 8 hours after
• Warfarin: Enhanced anticoagulant effect; monitor INR closely
• NSAIDs: May increase CNS stimulation and seizure risk
• Corticosteroids: Increased tendon rupture risk; avoid concurrent use when possible
• Sucralfate: Reduces moxifloxacin absorption; separate administration timing

Special Populations

• Renal Impairment: No dose adjustment required for any degree of renal dysfunction
• Hepatic Impairment: Use with caution in moderate-to-severe impairment; limited data available
• Pregnancy: Category C; use only if benefits outweigh potential fetal risks
• Pediatric: Not recommended due to musculoskeletal adverse effects in animal studies
• Elderly: Increased risk of tendon disorders and QT prolongation; monitor carefully