Does Moxifloxacin achieve therapeutic concentration in urine?

Moxifloxacin Does Not Achieve Therapeutic Concentrations in Urine

Moxifloxacin should be avoided for the treatment of urinary tract infections because of uncertainty regarding effective concentrations in urine. 1

Pharmacokinetic Properties and Urinary Excretion

Moxifloxacin has limited urinary excretion compared to other fluoroquinolones:

• Only approximately 20% of an oral or intravenous dose of moxifloxacin is excreted unchanged in urine 2
• The remaining drug is metabolized via glucuronide and sulfate conjugation, with about 45% of the dose excreted as unchanged drug (20% in urine and 25% in feces) 2
• Total body clearance and renal clearance are 12 ± 2 L/hr and 2.6 ± 0.5 L/hr, respectively 2

This contrasts sharply with other fluoroquinolones that achieve much higher urinary concentrations:

• Ofloxacin has a urinary excretion rate of 84.3% of the parent drug 3
• Gatifloxacin has been shown to have higher renal excretion than moxifloxacin 4

Clinical Implications for UTI Treatment

The Infectious Diseases Society of America (IDSA) specifically recommends against using moxifloxacin for urinary tract infections:

• "Moxifloxacin should be avoided for the treatment of UTI because of uncertainty regarding effective concentrations in urine." 1
• For catheter-associated UTIs, IDSA guidelines recommend other fluoroquinolones like levofloxacin (750 mg daily for 5 days) for patients who are not severely ill 1

Tissue Distribution vs. Urinary Concentration

While moxifloxacin has excellent tissue penetration in many body compartments:

• It is widely distributed throughout the body with tissue concentrations often exceeding plasma concentrations 2
• It shows high penetration into respiratory tissues, abdominal tissues, and other compartments 2
• It has demonstrated efficacy in intra-abdominal infections with clinical success rates of approximately 90% 1

However, its low urinary excretion makes it unsuitable for urinary tract infections where high concentrations of the active drug in urine are necessary for effective bacterial killing.

Alternative Fluoroquinolones for UTI Treatment

For urinary tract infections, other fluoroquinolones with higher urinary excretion are preferred:

• Levofloxacin (750 mg once daily for 5 days) is recommended for non-severe catheter-associated UTIs 1
• Ciprofloxacin (500 mg twice daily for 7 days) is another option in regions with low resistance 5

Important Clinical Considerations

When treating UTIs, clinicians should:

1. Choose antibiotics with high urinary concentrations
2. Consider local resistance patterns
3. Adjust treatment duration based on severity and patient factors
4. Remove urinary catheters when possible to facilitate treatment

Conclusion

Despite one small study suggesting moxifloxacin might be useful in urinary infections 6, the most authoritative and recent guidelines from the Infectious Diseases Society of America explicitly recommend against using moxifloxacin for UTIs due to insufficient urinary concentrations. Other fluoroquinolones with higher urinary excretion should be selected instead when treating urinary tract infections.