Is 500 mg of gentamicin (intravenous) appropriate for treating brucellosis?

Gentamicin Dosing for Brucellosis Treatment

For brucellosis treatment, 500 mg of gentamicin IV is not the recommended dose; instead, gentamicin should be dosed at 5 mg/kg daily parenterally in a single dose for 7 days, combined with doxycycline 100 mg twice daily orally for 6 weeks. 1, 2

Recommended Treatment Regimens for Brucellosis

First-Line Options:

• Doxycycline-Streptomycin: Doxycycline 100 mg twice daily orally for 6 weeks plus streptomycin 15 mg/kg daily intramuscularly for 2-3 weeks (AI recommendation) 1
• Doxycycline-Rifampicin: Doxycycline 100 mg twice daily orally for 6 weeks plus rifampicin 600-900 mg daily as a single morning dose for 6 weeks (AI recommendation) 1

Preferred Alternative Regimen:

• Doxycycline-Gentamicin: Doxycycline 100 mg twice daily orally for 6 weeks plus gentamicin 5 mg/kg daily parenterally in a single dose for 7 days (BI recommendation) 1, 2
  • This combination offers advantages over doxycycline-streptomycin due to wider availability of gentamicin and sparing streptomycin for tuberculosis treatment 1, 2
  • Studies have shown relapse rates comparable to WHO-recommended regimens 1, 3

Gentamicin Dosing Considerations

• The fixed dose of 500 mg gentamicin is not recommended in guidelines; weight-based dosing at 5 mg/kg daily is the standard 1, 2
• Duration should be 7 days when combined with doxycycline 1, 2
• Some studies suggest gentamicin duration could be shortened to 5 days or extended to 14 days for optimal results 1
• A recent study demonstrated that gentamicin at 5 mg/kg/day for one week is safe with minimal risk of nephrotoxicity in brucellosis patients 4

Treatment Efficacy Data

• Non-comparative studies using gentamicin for 5-7 days showed failure/relapse rates of 10-20%, which is approximately 5% higher than WHO-recommended regimens 1
• A randomized trial comparing gentamicin (5 mg/kg daily for 5 days) plus doxycycline (8 weeks) versus streptomycin (2 weeks) plus doxycycline (45 days) showed similar efficacy (95.12% vs 89%) 5
• Another study showed that doxycycline for 45 days plus gentamicin for 7 days had a lower relapse rate (5.9%) compared to doxycycline for 30 days plus gentamicin for 7 days (22.9%) 3

Important Clinical Considerations

• The combination of doxycycline and gentamicin is considered an adequate regimen with advantages over doxycycline-streptomycin 1, 2
• Gentamicin is effective against Brucella melitensis and can be used when the classical combination is considered first choice 6
• Monitor renal function when using gentamicin, although recent evidence suggests minimal nephrotoxicity risk at recommended doses 4
• In regions where brucellosis and tuberculosis coexist, gentamicin may be preferred over rifampicin to avoid contributing to mycobacterial resistance 2, 7

Treatment Duration

• Standard treatment duration is 6 weeks for doxycycline when combined with gentamicin for 7 days 1, 2
• Shortening doxycycline treatment to 30 days results in higher relapse rates (22.9%) compared to 45 days (5.9%) 3
• Relapse rates range from 5-15% even with appropriate treatment 2, 7

Remember that the appropriate treatment of brucellosis requires combination therapy, and fixed-dose gentamicin at 500 mg is not recommended by current guidelines. Weight-based dosing at 5 mg/kg daily for 7 days in combination with doxycycline for 6 weeks is the recommended approach.