Gentamicin Dosing for UTI
For uncomplicated UTIs requiring parenteral therapy, gentamicin should be administered at 5 mg/kg once daily, as recommended by the European Association of Urology guidelines. 1
Dosing Recommendations Based on UTI Type
Uncomplicated UTI
- Parenteral therapy: 5 mg/kg once daily 1
- Duration: 5-7 days (shorter course is effective while minimizing resistance and toxicity risks) 2
Complicated UTI
- Standard dosing: 3 mg/kg/day divided into 2-3 doses 3, 4
- Alternative once-daily dosing: 5 mg/kg once daily with close monitoring 1
- Duration: 7-14 days depending on clinical response
Therapeutic Drug Monitoring
Monitoring is essential to optimize efficacy while minimizing toxicity:
- Target peak serum concentration: 4-6 μg/mL 2
- Target trough serum concentration: <1 μg/mL (preferably <0.5 μg/mL) 2, 5
- Timing of levels:
- Peak: 30 minutes after completion of infusion
- Trough: Just before next dose
Special Populations
Renal Impairment
- Baseline renal function assessment is mandatory
- Regular monitoring of serum creatinine and BUN during treatment
- Dose adjustment based on creatinine clearance:
- For CrCl <50 mL/min: Consider extending dosing interval rather than reducing dose
- For severe impairment: Consider alternative antibiotics
Elderly Patients
- Lower initial dose (3-4 mg/kg/day)
- More frequent monitoring of renal function
- Consider extended interval dosing (every 36-48 hours) based on renal function
Obese Patients
- Use adjusted body weight for dosing calculations 5
Administration
- Intravenous administration: Infuse over 30 minutes
- Intramuscular administration: Appropriate alternative if IV access unavailable
Monitoring for Toxicity
- Nephrotoxicity: Monitor serum creatinine every 2-3 days
- Ototoxicity: Assess for hearing changes and vestibular symptoms
- Risk factors for toxicity: Pre-existing renal impairment, advanced age, concomitant nephrotoxic medications 2
Clinical Pearls
- Once-daily dosing may be as effective as multiple daily doses for UTIs while potentially reducing toxicity 6, 5
- For lower UTIs, a single daily dose of gentamicin has shown excellent efficacy 6
- Avoid concomitant use of other nephrotoxic drugs when possible
- Ensure adequate hydration during therapy to minimize nephrotoxicity
- Consider alternative antibiotics if treatment is expected to exceed 7 days
The European Association of Urology provides the most recent and authoritative guidance on gentamicin dosing for UTIs, recommending 5 mg/kg once daily 1. This approach balances efficacy against Gram-negative uropathogens with the need to minimize toxicity.