Fluoroquinolones: Ciprofloxacin & Levofloxacin Guide for Gram-Negative and Atypical Infections

Fluoroquinolones like Ciprofloxacin and Levofloxacin treat Gram-negative and atypical infections. Learn mechanism, spectrum, uses, side effects, and interactions.

Introduction

Fluoroquinolones are broad-spectrum, bactericidal antibiotics that inhibit bacterial DNA replication. They are effective against Gram-negative and some Gram-positive bacteria, including atypical pathogens. Common prototypes include Ciprofloxacin and Levofloxacin.

Medications in the Class

• Ciprofloxacin (prototype)

• Levofloxacin

• Moxifloxacin

• Ofloxacin

• Norfloxacin

Mechanism of Action

Fluoroquinolones block DNA gyrase (topoisomerase II) and topoisomerase IV. This stops bacterial DNA from replicating, transcribing, and repairing. This leads to bacterial death.

Spectrum of Activity

• Gram-negative bacteria: E. coli, Klebsiella, Pseudomonas aeruginosa (Ciprofloxacin > Levofloxacin)

• Gram-positive bacteria: Streptococcus pneumoniae (Levofloxacin, Moxifloxacin)

• Atypical pathogens: Mycoplasma, Chlamydia, Legionella

• Anaerobes: Moxifloxacin has limited activity

• Not effective against: MRSA (except some newer agents), Enterococci

Indications (When Used)

• Urinary tract infections and pyelonephritis

• Respiratory infections: CAP, HAP

• Gastrointestinal infections: traveler’s diarrhea, typhoid

• Bone and joint infections

• Anthrax prophylaxis and treatment (Ciprofloxacin)

Contraindications (When Not to Use)

• Children <18 years and pregnant women (risk of tendon/cartilage damage)

• Known hypersensitivity

• History of tendon disorders related to fluoroquinolones

Side Effects

• Gastrointestinal upset: nausea, vomiting, diarrhea

• Tendonitis and tendon rupture (Achilles tendon)

• CNS: headache, dizziness, seizures (rare)

• QT prolongation (especially Moxifloxacin)

• Photosensitivity

Drug Interactions

• Antacids, calcium, magnesium, iron: decrease absorption

• Warfarin: enhanced anticoagulant effect

• Antiarrhythmics: increased risk of QT prolongation

• CYP1A2 substrates: Ciprofloxacin may increase serum levels of theophylline, caffeine

Antidote

No specific antidote. Supportive care and drug discontinuation for severe reactions.

Monitoring of Potential Complications

• Tendon pain: discontinue immediately if occurs

• Renal function in elderly or prolonged therapy

• ECG monitoring in patients at risk of QT prolongation

• Liver function tests in long-term therapy

Fluoroquinolones are broad-spectrum, potent antibiotics for serious Gram-negative and atypical infections. Monitoring for tendon, cardiac, and CNS complications is essential for safe therapy.