Should I give the next dose of amikacin when the serum concentration is 11.7 µg/mL?

Should You Give the Next Dose of Amikacin with a Level of 11.7 µg/mL?

No, you should hold the next dose of amikacin when the trough level is 11.7 µg/mL, as this exceeds the maximum safe trough concentration of 10 µg/mL and places the patient at significant risk for nephrotoxicity and ototoxicity. 1

Critical Threshold Exceeded

• Trough concentrations above 10 µg/mL must be avoided according to FDA labeling, which explicitly states that dosing should be adjusted when trough levels (measured just prior to the next dose) exceed this threshold 1
• The level of 11.7 µg/mL represents drug accumulation that significantly increases toxicity risk without improving efficacy 1

Immediate Management Steps

Hold the dose and reassess:

• Do not administer the scheduled dose until the level falls below 10 µg/mL 1
• Measure serum creatinine immediately to assess for early nephrotoxicity, as renal impairment occurs in 8.7% of patients overall and is the most common cause of elevated trough levels 2
• Question the patient about auditory symptoms (tinnitus, hearing loss) and vestibular symptoms (dizziness, imbalance), as ototoxicity risk increases substantially with elevated troughs 2

Dosing Adjustment Strategy

When resuming therapy, adjust the dosing interval, not the dose:

• The fundamental principle is to reduce frequency while maintaining the individual milligram dose to preserve concentration-dependent bactericidal activity 3, 2
• If renal function is impaired (elevated creatinine), extend the dosing interval to every 24-48 hours or 2-3 times weekly at 12-15 mg/kg per dose 3
• Never reduce the milligram dose as this compromises efficacy—smaller doses reduce drug effectiveness 3, 2

Calculate Appropriate Interval

If the patient's creatinine clearance is reduced or serum creatinine is elevated:

• A practical formula: multiply the patient's serum creatinine (mg/dL) by 9 to determine the dosing interval in hours 1
• For example, if serum creatinine is 2.0 mg/dL, administer the normal dose (7.5 mg/kg) every 18 hours 1
• For patients on hemodialysis, give the dose after dialysis at 12-15 mg/kg two to three times weekly 3

Monitoring Requirements Going Forward

Mandatory assessments to prevent further accumulation:

• Measure both peak (30-90 minutes post-dose) and trough levels with every dosing adjustment 1
• Peak concentrations should remain below 35 µg/mL 1
• Trough concentrations must stay below 10 µg/mL 1
• Check serum creatinine at least twice weekly during therapy 2
• Assess for auditory/vestibular symptoms at each clinical encounter 2

High-Risk Factors to Consider

Identify why accumulation occurred:

• Baseline renal impairment is the most common cause and increases both nephrotoxicity and ototoxicity risk 2
• Elderly patients (>59 years) have reduced renal reserve and require dose reduction to 10 mg/kg per day 3
• Concurrent nephrotoxic medications (NSAIDs, vancomycin, contrast agents) amplify toxicity risk 2
• Cumulative dose exposure—patients receiving prolonged courses have progressively higher toxicity rates 2

Critical Pitfall to Avoid

Never administer amikacin before hemodialysis if the patient is on dialysis, as this removes the drug prematurely and causes treatment failure while still exposing the patient to toxicity 3, 2. Always give the dose after dialysis 3.