Ofloxacin-Ornidazole Dosage for Bacterial and Protozoal Infections
For adults with mixed bacterial and protozoal infections, administer ofloxacin 200-400 mg orally twice daily combined with ornidazole 500 mg twice daily, with the specific dose and duration determined by the infection type and severity. 1
Standard Adult Dosing Regimens
Ofloxacin Dosing by Indication
Gastrointestinal infections (including bacterial diarrhea):
- 200 mg orally twice daily for 5-7 days for acute intestinal infections including dysentery and salmonellosis 2, 3
- May start with IV administration for first 2 days (200 mg IV twice daily) followed by oral therapy for severe cases 2
Genitourinary infections:
- Uncomplicated cystitis: 200 mg twice daily for 3-7 days depending on pathogen 1
- Complicated UTIs: 200 mg twice daily for 10 days 1
- Nongonococcal urethritis/cervicitis (Chlamydia): 300 mg twice daily for 7 days 4, 1
- Acute pelvic inflammatory disease: 400 mg twice daily for 10-14 days (must add metronidazole for anaerobic coverage) 5, 4
Respiratory infections:
- Acute bacterial exacerbation of chronic bronchitis or community-acquired pneumonia: 400 mg twice daily for 10 days 1
Skin and soft tissue infections:
- 400 mg twice daily for 10 days 1
Ornidazole Dosing
For protozoal infections (Giardia, Entamoeba):
- 500 mg orally twice daily is the typical adult dose when combined with ofloxacin 6
- Single daily dosing of 1-2 grams may be used for certain protozoal infections, though twice-daily dosing is more common in combination therapy
Pediatric Dosing Considerations
Ofloxacin in children should be reserved for specific situations (multidrug-resistant tuberculosis, intolerance to first-line agents) due to cartilage development concerns 7
When fluoroquinolones are necessary:
- 7.5 mg/kg every 12 hours (maximum 400 mg/dose) for most infections 7
- For MDR-TB: 15-20 mg/kg/day (maximum 1.0 g/day) as single or divided dose 7
Ornidazole pediatric dosing:
- 20-30 mg/kg as a single daily dose 7
Critical pediatric restrictions:
- Avoid in children <1 month of age 7
- Not recommended for long-term use (>several weeks) due to bone/cartilage effects 7
- Contraindicated in children ≤17 years for routine infections 4
Critical Administration Guidelines
Timing with other medications:
- Do not administer within 2 hours before or after antacids containing calcium/magnesium/aluminum, sucralfate, iron supplements, zinc-containing multivitamins, or didanosine 1, 7
- This interaction significantly decreases fluoroquinolone absorption 7
Food considerations:
- Ofloxacin can be taken with or without food 1
- Ornidazole absorption is not significantly affected by food
Renal Dosing Adjustments
For creatinine clearance ≤50 mL/min, adjust ofloxacin dosing: 1
- CrCl 20-50 mL/min: Give usual dose every 24 hours (instead of every 12 hours)
- CrCl <20 mL/min: Give half the usual dose every 24 hours
- No supplemental dose needed after hemodialysis 7
Ornidazole does not require renal dose adjustment in most cases, though caution is advised in severe renal impairment.
Hepatic Dosing Adjustments
For severe liver dysfunction (cirrhosis with or without ascites):
- Maximum 400 mg ofloxacin per day 1
- Ornidazole should be used cautiously; consider dose reduction in severe hepatic impairment
Common Pitfalls and Safety Considerations
Inadequate anaerobic coverage:
- Ofloxacin alone lacks adequate anaerobic coverage 5
- Always add metronidazole or ornidazole for mixed aerobic-anaerobic infections, particularly pelvic inflammatory disease and intra-abdominal infections 5
Pregnancy and lactation:
- Absolutely contraindicated in pregnant women 4
- Avoid during breastfeeding
Monitoring requirements:
- Regular monitoring for adverse effects with prolonged use 7
- Watch for tendon rupture risk (increased with corticosteroid use, age >60 years)
- Monitor for QT prolongation, especially with concurrent QT-prolonging medications
Treatment completion:
- Patients must complete the full course even if symptoms improve early 4
- Re-evaluate if no improvement within 3 days 4
Comparative Efficacy Notes
While ofloxacin-ornidazole combinations are marketed for mixed bacterial-protozoal infections 6, metronidazole remains superior to ofloxacin for bacterial vaginosis (56% vs 23% cure rate at end of treatment) due to better anaerobic coverage 8. For chronic osteomyelitis, ofloxacin shows comparable efficacy to parenteral antibiotics (74% vs 86% long-term success) with advantages in convenience and cost 9.