For a typical adult with normal renal function, should Norfloxacin be given once daily or twice daily?

Norfloxacin Dosing: Once Daily vs Twice Daily

Norfloxacin should be given as 400 mg twice daily (BD) for most urinary tract infections, as this is the standard dosing regimen supported by international guidelines and clinical trials. 1

Standard Dosing Regimen

For uncomplicated cystitis in women, norfloxacin 400 mg twice daily for 3 days is the recommended regimen, achieving bacterial cure rates of 91% and clinical cure rates of 88%. 1

For complicated urinary tract infections, norfloxacin 400 mg twice daily should be continued for 10-21 days, with comparable efficacy to ciprofloxacin. 2

Evidence for Once Daily vs Twice Daily Dosing

A small randomized trial directly compared norfloxacin 800 mg once daily versus 400 mg twice daily and found similar bacterial and clinical outcomes, though the study had limited statistical power to detect true differences. 1

A larger trial in 86 women with uncomplicated UTI demonstrated that norfloxacin 800 mg once daily achieved 92% bacteriological efficacy compared to 95.5% with 400 mg twice daily, with no statistically significant difference. 3 Clinical efficacy was 95.3% versus 100%, respectively. 3

Practical Dosing Algorithm

For uncomplicated cystitis:

• First choice: 400 mg twice daily for 3 days 1
• Alternative (if compliance is a concern): 800 mg once daily for 3 days 3

For complicated UTI or pyelonephritis:

• Standard regimen: 400 mg twice daily for 10 days 1
• Once daily dosing has not been adequately studied for complicated infections

For prophylaxis in cirrhotic patients:

• 400 mg once daily (single-dose norfloxacin) is used for selective intestinal decontamination 1

Important Clinical Considerations

The twice-daily regimen (400 mg BD) remains the guideline-recommended standard because it has been more extensively studied and validated in large clinical trials. 1 The once-daily regimen (800 mg OD) appears equivalent for uncomplicated UTI but lacks robust data for serious infections. 3

Common pitfall: Using once-daily dosing for complicated infections or pyelonephritis without adequate evidence of efficacy. The 10-day course of norfloxacin 400 mg twice daily for pyelonephritis resulted in lower bacterial relapse rates compared to other agents. 1

Fluoroquinolone resistance is an increasing concern, and norfloxacin should be reserved for situations where local resistance patterns support its use. 1 The drug achieves high urinary concentrations, making it particularly effective for urinary tract infections. 4