Quinolones
Quinolones are synthetic, broad-spectrum, bactericidal antibiotics that inhibit bacterial DNA replication and transcription by targeting key enzymes. They are beta-lactamase resistant.
Classification / Examples
- 1st Gen: Nalidixic acid
- 2nd Gen: Norfloxacin, Ofloxacin, Ciprofloxacin
- 3rd Gen: Levofloxacin
- 4th Gen: Delafloxacin, Moxifloxacin
Pharmacodynamics
- Quinolones inhibit DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes critical for:
- Supercoiling and uncoiling of bacterial DNA
- Separation of replicated DNA into daughter cells
- This interference causes:
- DNA strand breaks
- Disruption of replication and transcription
- Bacterial cell death (bactericidal action)
- Broad-spectrum: active against Gram-negative, Gram-positive, and atypical pathogens
- Resistant to β-lactamase enzymes
Side Effects
- Common:
- GI: nausea, abdominal pain, diarrhea
- CNS: headache, dizziness
- Serious:
- Tendonitis, Achilles tendon rupture (especially in elderly, steroid users)
- Peripheral neuropathy (numbness, tingling)
- QT prolongation → risk of torsades de pointes
- Severe hypersensitivity: SJS, TEN
- CNS effects: insomnia, agitation, rarely seizures
Drug Interactions
- ↑ QT prolongation with:
- Antiarrhythmics (amiodarone)
- Antipsychotics, some antidepressants
- ↑ Tendon rupture risk with corticosteroids
- ↓ Absorption with:
- Antacids, sucralfate, calcium, magnesium, iron supplements
- ↑ Warfarin effect → ↑ bleeding risk
- ↑ CNS stimulation and seizures with NSAIDs