What ciprofloxacin dosing interval and duration is recommended for an otherwise healthy adult with suspected bacterial food‑borne gastroenteritis (e.g., Campylobacter, Shigella, non‑typhoidal Salmonella, or enterotoxigenic E. coli)?

Ciprofloxacin Dosing for Bacterial Food Poisoning

For otherwise healthy adults with suspected bacterial food-borne gastroenteritis, ciprofloxacin 500 mg orally twice daily for 5–7 days is the recommended regimen, though azithromycin is now preferred first-line for Campylobacter due to widespread fluoroquinolone resistance. 1

Standard Dosing Regimen

The FDA-approved dose for infectious diarrhea is ciprofloxacin 500 mg orally every 12 hours for 5–7 days. 1 This regimen applies to mild, moderate, and severe bacterial gastroenteritis in adults. 1

• Oral route: 500 mg twice daily for 5–7 days 1
• Intravenous route (for severe cases requiring hospitalization): 400 mg IV every 12 hours 2, 1
• Treatment should continue for at least 2 days after signs and symptoms resolve 1

Pathogen-Specific Considerations

Non-typhoidal Salmonella

• Ciprofloxacin 500 mg orally twice daily is effective and appropriate 2
• Alternative oral agents include levofloxacin 500 mg once daily, amoxicillin 500 mg three times daily, or TMP-SMX 160/800 mg twice daily, depending on susceptibility 2
• Clinical studies demonstrate ciprofloxacin reduces diarrhea duration from 3.2 days to 1.6 days in salmonellosis 3

Shigella

• Fluoroquinolones remain an option (ciprofloxacin 500 mg twice daily orally or 400 mg twice daily IV), but azithromycin 500 mg once daily is increasingly preferred due to rising resistance 2
• Ciprofloxacin achieves negative stool cultures within 48 hours in susceptible strains 3

Campylobacter

• Azithromycin 500 mg once daily is now first-line therapy due to fluoroquinolone resistance rates exceeding 70–90% in many regions 4, 5
• Ciprofloxacin should only be used if local resistance is <10% 4, 5
• Clinical failure occurs in approximately 33% of patients treated with fluoroquinolones when the isolate is resistant 4

Enterotoxigenic E. coli (ETEC)

• Ciprofloxacin 500 mg twice daily for 1–3 days is highly effective for traveler's diarrhea caused by ETEC 6, 7
• Shorter 1–3 day courses are often sufficient for uncomplicated ETEC 6

Yersinia

• Ciprofloxacin 500 mg orally twice daily or 400 mg IV twice daily is recommended 2
• Alternative: TMP-SMX 160/800 mg twice daily or doxycycline 100 mg twice daily 2

Duration of Therapy

The standard duration is 5–7 days for most bacterial gastroenteritis. 1 However:

• Shorter courses (1–3 days) may suffice for uncomplicated traveler's diarrhea caused by ETEC 6
• Longer courses (7–14 days) may be needed for severe or complicated infections 1
• Immunocompromised patients may require extended therapy (14–21 days) 4

Dose Adjustments for Renal Impairment

Creatinine Clearance	Dose	Frequency
>50 mL/min	500 mg	Every 12 hours [1]
30–50 mL/min	250–500 mg	Every 12 hours [1]
5–29 mL/min	250–500 mg	Every 18 hours [1]
Hemodialysis	250–500 mg	Every 24 hours (after dialysis) [1]

Critical Contraindications

Do NOT use ciprofloxacin (or any antibiotic) for suspected Shiga-toxin-producing E. coli (STEC/O157:H7), as antibiotics increase the risk of hemolytic-uremic syndrome. 4, 5

• Avoid in children unless severe β-lactam allergy exists; third-generation cephalosporins or azithromycin are preferred 5
• Avoid in pregnancy; azithromycin is safer 5
• Avoid for viral gastroenteritis (norovirus, rotavirus), which accounts for most acute diarrhea cases 2, 5

When to Choose Azithromycin Over Ciprofloxacin

Azithromycin should be preferred in the following scenarios:

• Recent travel to South/Southeast Asia where fluoroquinolone resistance exceeds 90% 4, 5
• Suspected or confirmed Campylobacter infection 4, 5
• Pregnancy 5
• Pediatric patients (when antibiotics are indicated) 5
• Areas with documented high fluoroquinolone resistance in local surveillance data 4, 5

Common Pitfalls to Avoid

• Do not treat asymptomatic Salmonella carriers with antibiotics, as this may prolong carriage 5
• Do not use antimotility agents (loperamide) with suspected invasive bacterial diarrhea (fever, bloody stools), as they worsen outcomes 4, 5
• Do not assume ciprofloxacin efficacy without considering local resistance patterns; resistance rates vary dramatically by region and pathogen 4, 5
• Do not use ciprofloxacin empirically for all food poisoning; most cases are viral and self-limited, requiring only supportive care 2, 5

Administration Timing

Ciprofloxacin must be taken at least 2 hours before or 6 hours after antacids containing magnesium/aluminum, sucralfate, calcium, iron, or zinc supplements, as these significantly reduce absorption 1