Ciprofloxacin Dosing for Typhoid Fever in Adults
For uncomplicated typhoid fever in adults, prescribe ciprofloxacin 500 mg orally every 12 hours for 10-14 days, not 200 mg or 400 mg tablets. The FDA-approved dosing for typhoid fever is specifically 500 mg twice daily for 10 days 1.
Standard Dosing Regimen
- Ciprofloxacin 500 mg orally every 12 hours for 10 days is the FDA-approved regimen for typhoid fever in adults 1
- Clinical trials demonstrate that 500 mg twice daily for 10 days achieves 100% cure rates with mean defervescence time of 4.2 days 2
- The 14-day regimen (500 mg twice daily) shows equivalent efficacy to the 10-day course, with no significant difference in fever clearance time (4.9 vs 4.2 days) 2
Why Not 200 mg or 400 mg?
- The 200 mg and 400 mg formulations are intravenous preparations, not oral tablets for typhoid fever 1
- Oral ciprofloxacin tablets are manufactured as 250 mg, 500 mg, and 750 mg strengths 1
- Using suboptimal doses (such as 200 mg or 400 mg daily) risks treatment failure, particularly with the rising prevalence of nalidixic acid-resistant strains that already show reduced ciprofloxacin susceptibility 3
Critical Warnings About Ciprofloxacin Resistance
- Exercise extreme caution when treating travelers returning from India, as fluoroquinolone-resistant Salmonella typhi strains with decreased susceptibility are increasingly common 4
- Clinical failures occur even when isolates test "susceptible" in vitro (MIC 0.75 μg/mL), with patients requiring 13 days of ciprofloxacin 500 mg every 12 hours before switching to ceftriaxone 3
- In Bangladesh, ciprofloxacin showed only 62% clinical cure rates for multidrug-resistant, nalidixic acid-resistant strains, compared to 85% with azithromycin 5
When Ciprofloxacin Fails
- If fever persists beyond 5-7 days on ciprofloxacin 500 mg twice daily, switch to intravenous ceftriaxone 1-2 g every 12-24 hours 6, 3
- Patients typically respond to ceftriaxone within 3 days when ciprofloxacin fails 3
- All ciprofloxacin treatment failures in documented cases responded completely to ceftriaxone therapy 6
Administration Considerations
- Administer ciprofloxacin at least 2 hours before or 6 hours after antacids, calcium, iron, or zinc supplements, as these markedly decrease fluoroquinolone absorption 1
- Avoid in pregnancy due to teratogenic effects; select alternative agents for pregnant patients 4
- For creatinine clearance <50 mL/min, reduce dosing frequency or dose to prevent accumulation 4
Alternative First-Line Options
Given the declining efficacy of ciprofloxacin in many endemic regions, consider:
- Azithromycin 20 mg/kg/day (or 500 mg daily in adults) for 7-14 days shows superior clinical cure rates (85%) and faster fever clearance (5.8 days) compared to ciprofloxacin (8.2 days) for multidrug-resistant strains 5
- Cefixime 400 mg twice daily for 14 days demonstrates 71% cure rates for resistant strains 5
Common Pitfall to Avoid
Do not confuse IV and oral dosing equivalents. The 400 mg IV dose every 12 hours is equivalent to 500 mg oral every 12 hours due to bioavailability differences, but you should prescribe the oral 500 mg tablets for outpatient typhoid treatment, not attempt to use IV formulations orally 1.