What are the uses and dosages of the Quinolones (fluoroquinolones) group of drugs, including ciprofloxacin (Cipro), levofloxacin (Levaquin), and moxifloxacin (Avelox)?

Quinolones (Fluoroquinolones): Uses and Dosages

Fluoroquinolones are broad-spectrum antibiotics that should be used only when no safe and effective alternatives exist due to their significant adverse effect profile, including tendinopathy and tendon rupture. 1, 2

Classification and Spectrum of Activity

• First generation: Nalidixic acid - limited spectrum, approved for children ≥3 months 1
• Second generation: Ciprofloxacin, levofloxacin, norfloxacin, ofloxacin - greater Gram-negative spectrum including Pseudomonas aeruginosa 1
• Third generation: Gemifloxacin - increased activity against Streptococcus pneumoniae while maintaining Gram-negative coverage 1
• Fourth generation: Moxifloxacin - increased anaerobic activity while maintaining Gram-positive and Gram-negative coverage 1

Primary Indications

Respiratory Tract Infections

• Levofloxacin and moxifloxacin are recommended for community-acquired pneumonia in adults with comorbidities or recent antibiotic exposure 1
• Moxifloxacin is approved for community-acquired pneumonia and acute exacerbations of chronic bronchitis 1
• Fluoroquinolones are not first-line for simple respiratory infections but may be used when resistance to first-line agents is suspected 1

Tuberculosis

• Levofloxacin and moxifloxacin show significant efficacy in multidrug-resistant tuberculosis (MDR-TB) treatment regimens 1
• Associated with significantly more treatment success (aOR 4.2 for levofloxacin, 3.8 for moxifloxacin) and fewer deaths compared to regimens without fluoroquinolones 1

Intra-abdominal Infections

• Moxifloxacin monotherapy is recommended by IDSA for mild-to-moderate complicated intra-abdominal infections 1
• Not recommended as empiric therapy in regions with high rates (>20%) of fluoroquinolone resistance among E. coli 1

Urinary Tract Infections

• Ciprofloxacin is effective for complicated and uncomplicated UTIs 2
• Levofloxacin is as effective as ofloxacin in uncomplicated UTIs and comparable to ciprofloxacin in complicated UTIs 3

Specific Dosages

Ciprofloxacin (Cipro)

• UTIs: 250-500 mg PO twice daily 2
• Respiratory infections: 500-750 mg PO twice daily 2
• Complicated skin infections: 500-750 mg PO twice daily 2

Levofloxacin (Levaquin)

• Community-acquired pneumonia: 750 mg PO/IV once daily for 5 days or 500 mg once daily for 7-14 days 3
• Complicated UTIs: 250-500 mg PO once daily for 7-10 days 3
• Chronic bacterial prostatitis: 500 mg PO once daily for 28 days 3
• MDR-TB: 15-20 mg/kg daily for children 1

Moxifloxacin (Avelox)

• Community-acquired pneumonia: 400 mg PO/IV once daily for 7-14 days 4
• Acute bacterial sinusitis: 400 mg PO once daily for 10 days 1
• Complicated skin infections: 400 mg PO/IV once daily 4
• MDR-TB: 10-15 mg/kg/day for children 1

Safety Considerations

Major Warnings

• Tendinopathy and tendon rupture: Increased risk in all ages, particularly those >60 years, patients on corticosteroids, and those with kidney, heart, or lung transplants 2
• CNS effects: Convulsions, increased intracranial pressure, toxic psychosis, dizziness, confusion, and rarely suicidal thoughts 2
• QT interval prolongation: Particularly with moxifloxacin; avoid in patients with known QT prolongation, uncorrected electrolyte abnormalities, or taking Class IA or III antiarrhythmics 1, 5
• Hypersensitivity reactions: Including anaphylaxis, sometimes after the first dose 2
• C. difficile-associated diarrhea: Can range from mild diarrhea to fatal colitis 2

Special Populations

• Elderly: Require dose adjustment based on renal function; increased risk of tendinopathy and CNS effects 5, 6
• Pediatrics: Limited use due to risk of arthropathy; ciprofloxacin approved for children 1-17 years for specific indications only 1, 2
• Pregnancy: Safety not established; should be used only if potential benefit justifies risk 2

Administration Considerations

• Take on an empty stomach when possible 1
• Avoid coadministration with metal ion-containing products (antacids, supplements with magnesium, aluminum, iron, calcium) 1
• Monitor for drug interactions, especially with drugs metabolized by CYP1A2 (e.g., theophylline) 2

Resistance Concerns

• Increasing resistance rates necessitate judicious use 1
• Later-generation fluoroquinolones (levofloxacin, moxifloxacin) show better efficacy against resistant strains compared to earlier agents like ofloxacin 1
• Should be reserved for infections where no safe and effective alternative exists 1