Amikacin Therapeutic Drug Monitoring for Non-Tuberculous Mycobacterial Infection
For intravenous amikacin in NTM infections, both peak and trough levels should be monitored, not trough alone. 1
Monitoring Strategy
The British Thoracic Society guidelines for NTM pulmonary disease explicitly recommend monitoring both peak and trough levels for IV amikacin 1:
Target Levels
- Trough: <5 mg/L (predose)
- Peak:
- 25–35 mg/L for daily dosing
- 65–80 mg/L for three-times-weekly dosing
Timing and Frequency
Peak level measurement:
- Obtain in the first week of therapy
- Take level 90–120 minutes after infusion ends AND at 6 hours, then plot on semilogarithmic paper and extrapolate back to time=0 for true peak
- Alternatively, a level at 60 minutes post-infusion may be used but will underestimate the true peak
- Repeat if poor clinical response
Trough level measurement:
- Weekly for the first 4 weeks
- Reduce to fortnightly once stable
Rationale for Both Levels
The dual monitoring approach serves distinct clinical purposes 1, 2:
Peak levels ensure therapeutic efficacy because amikacin exhibits concentration-dependent bactericidal activity. Low peaks indicate inadequate dosing requiring dose increases. High peaks (>35 mg/L for daily dosing) necessitate dose reduction to prevent toxicity.
Trough levels detect drug accumulation, particularly in renal impairment. Elevated troughs (>5 mg/L) indicate the need to extend dosing intervals to prevent nephrotoxicity and ototoxicity.
Dosage Adjustments Based on Levels
- High trough: Extend dosing interval
- High peak: Reduce dose
- Low peak: Increase dose 1
Critical Safety Considerations
The FDA label emphasizes that peak concentrations above 35 mcg/mL and trough concentrations above 10 mcg/mL should be avoided 2. The guideline targets are more conservative (trough <5 mg/L), reflecting the prolonged treatment duration typical for NTM infections compared to other indications.
Common pitfall: Monitoring trough alone misses subtherapeutic peaks, which may lead to treatment failure in NTM infections where achieving adequate drug exposure is essential for mycobacterial eradication 1.
Recent research suggests AUC24 monitoring may correlate better with clinical outcomes 3, but current guidelines have not yet incorporated this approach into standard practice. Until further evidence emerges, the established peak-and-trough monitoring strategy remains the standard of care 1.
For nebulized amikacin in NTM, only trough monitoring is recommended (target <5 mg/L) to ensure systemic accumulation is not occurring 1.