Target Trough Level for Amikacin
The target trough level for amikacin should be less than 5 mg/L to minimize toxicity while maintaining therapeutic efficacy. 1
Monitoring Recommendations
- Trough levels should be measured predose, with a recommended check 1 week after starting amikacin therapy 1
- Peak concentrations (measured 30-90 minutes after injection) should not exceed 35 μg/mL 2
- Trough concentrations (measured just prior to the next dose) should be maintained below 5 mg/L to prevent accumulation and reduce the risk of nephrotoxicity 1, 3
- If trough levels are high (>5 mg/L), the dosing interval should be extended rather than reducing the dose 1
Clinical Implications of Trough Monitoring
- Monitoring trough levels ensures that drug accumulation is not occurring, particularly in patients with renal impairment 1
- Elevated trough levels (>5 mg/L) are associated with increased risk of nephrotoxicity and ototoxicity 3, 2
- Regular monitoring of renal function is essential, with monthly assessments recommended (more frequent if renal impairment is present) 1
- Auditory and vestibular monitoring is also necessary as ototoxicity is a significant risk with amikacin therapy 1
Dosing Considerations
- Standard dosing for adults is 15 mg/kg/day, which can be administered as a single daily dose or divided (7.5 mg/kg q12h or 5 mg/kg q8h) 2
- For nebulized amikacin (used in non-tuberculous mycobacterial pulmonary disease), the dose is typically 500 mg twice daily 1
- In patients with renal impairment, dose adjustment is necessary to maintain appropriate trough levels 2
- Obese patients should have dosing calculated using ideal body weight plus 40% of excess weight 3
Common Pitfalls and Caveats
- Failure to monitor trough levels can lead to drug accumulation and increased toxicity 1, 2
- Patients with pre-existing renal impairment are at higher risk for developing acute kidney injury during amikacin therapy 4
- Elderly patients are particularly susceptible to nephrotoxicity and ototoxicity and may require closer monitoring 1, 5
- Concomitant use of other nephrotoxic medications (loop diuretics, other aminoglycosides, capreomycin, cephalosporins, ciclosporin, colistimethate sodium, tacrolimus) increases the risk of adverse effects 1
- Therapeutic drug monitoring is essential due to the wide interindividual variability in pharmacokinetics 6, 7
Special Populations
- In pediatric patients, when amikacin is used for synergy (such as in infective endocarditis), trough levels should be maintained at <1 μg/mL 1
- For treatment of gram-negative infections in children, trough levels should still be kept below 5 mg/L 8
- In critically ill patients with sepsis, higher loading doses may be needed due to increased volume of distribution, but trough monitoring remains essential to prevent toxicity 4, 6