What is the dose of levofloxacin (a fluoroquinolone antibiotic) for acute gastroenteritis in adults?

Levofloxacin Dosing for Acute Gastroenteritis in Adults

Primary Recommendation

For acute gastroenteritis in adults, levofloxacin 500 mg once daily orally is the recommended dose when a fluoroquinolone is indicated, though azithromycin should be strongly preferred as first-line therapy due to widespread fluoroquinolone resistance in common enteric pathogens. 1

Clinical Context and Pathogen-Specific Dosing

When Levofloxacin May Be Appropriate

Levofloxacin retains efficacy primarily for non-dysenteric watery diarrhea caused by diarrheagenic E. coli in regions without high fluoroquinolone resistance rates. 1 However, critical caveats exist:

• For dysentery (bloody diarrhea): Azithromycin is superior and should be first-line due to extremely high rates (>90%) of fluoroquinolone-resistant Campylobacter species globally. 1
• For febrile diarrhea: Azithromycin is preferred given the increased likelihood of fluoroquinolone-resistant Campylobacter, Shigella, and other invasive pathogens. 1

Specific Pathogen Dosing (When Identified)

For immunocompromised or cancer patients with confirmed bacterial gastroenteritis:

• Nontyphoidal Salmonella diarrhea: Levofloxacin 500 mg once daily orally 1
• Shigella diarrhea: Levofloxacin 500 mg once daily orally (though azithromycin 500 mg once daily is equally recommended) 1
• Yersinia diarrhea: Levofloxacin 500 mg once daily orally 1
• Campylobacter diarrhea: Azithromycin 500 mg once daily is strongly preferred; levofloxacin 500 mg once daily is listed as an alternative but has 19% resistance rates 1

Duration of Therapy

The standard duration is 3 days for acute gastroenteritis. 1, 2 Single-dose regimens (500 mg once) have demonstrated equivalent efficacy for acute watery non-invasive diarrhea in travelers' diarrhea studies. 1

Critical Resistance Considerations

Fluoroquinolone resistance is a major limitation:

• Campylobacter resistance exceeds 90% in Thailand and is increasingly reported in industrialized countries. 1
• Nalidixic acid and fluoroquinolone resistance in Shigella and Salmonella is emerging from India and sub-Saharan Africa. 1
• Treatment failures requiring rescue therapy occur in approximately 5% of cases even in settings with lower resistance. 1

Renal Dose Adjustments

Levofloxacin is 80% renally cleared and requires dose modification in renal impairment: 3

• CrCl ≥50 mL/min: No adjustment needed (500 mg once daily)
• CrCl <50 mL/min: Reduce to 750-1000 mg three times weekly 3
• Hemodialysis: No supplemental doses needed as levofloxacin is not cleared by dialysis 3

Drug Interactions and Administration

Levofloxacin must not be administered within 2 hours of antacids or medications containing divalent cations (calcium, magnesium, aluminum, iron), as these markedly decrease fluoroquinolone absorption. 3

Contraindications

Avoid levofloxacin in pregnancy due to teratogenic effects, which is a class effect of fluoroquinolones. 3

Common Pitfalls to Avoid

• Do not use levofloxacin empirically for dysentery or febrile gastroenteritis without considering azithromycin first, as resistance patterns make treatment failure likely. 1
• Do not use fluoroquinolones as first-line agents when azithromycin or rifaximin are appropriate alternatives. 1
• Do not forget to separate administration from antacids and supplements containing divalent cations by at least 2 hours. 3
• Do not use in patients with recent fluoroquinolone exposure, as this may indicate pre-existing resistance. 1

Adjunctive Therapy

Loperamide in combination with antibiotic treatment further reduces gastrointestinal symptoms and duration of illness in acute watery diarrhea. 2