Amikacin Dosing

For adults with normal renal function, administer amikacin 15 mg/kg/day (maximum 1.5 g/day) as a single daily dose or divided into 7.5 mg/kg every 12 hours or 5 mg/kg every 8 hours, with dose reduction to 10 mg/kg/day (750 mg) for patients over 59 years of age. 1

Adult Dosing

Standard Dosing for Normal Renal Function

15 mg/kg/day is the standard adult dose, administered intramuscularly or intravenously 2, 1
Can be given as:
- Single daily dose (15 mg/kg once daily) - preferred approach 1, 3
- Divided dosing: 7.5 mg/kg every 12 hours OR 5 mg/kg every 8 hours 1
Maximum daily dose: 1.5 g/day regardless of weight 1
Once-daily dosing achieves higher cure rates (83% vs 66%) and less nephrotoxicity (21% vs 35%) compared to twice-daily dosing 3

Age-Related Dose Adjustment

Patients >59 years: Reduce dose to 10 mg/kg/day (750 mg) due to age-related decline in renal function 2, 4
Elderly patients often have reduced creatinine clearance and should receive 11 mg/kg when using once-daily dosing 5, 6

Loading Dose Considerations

For critically ill patients or those requiring rapid therapeutic levels, consider a loading dose of 20 mg/kg 3
This is particularly important in patients with augmented renal clearance or increased volume of distribution 7

Pediatric Dosing

Infants and Children (>1 year)

15-30 mg/kg/day (maximum 1 g/day) as a single daily dose, intramuscularly or intravenously 2
Alternative: 15-22.5 mg/kg/day divided every 8 hours (5-7.5 mg/kg every 8 hours) 8
For severe infections or documented need based on serum levels: 30 mg/kg/day divided every 8 hours 8

Neonatal Dosing (Stratified by Weight and Age)

Loading dose: 10 mg/kg, followed by 7.5 mg/kg every 12 hours 1
<1200 grams, ≤7 days: 7.5 mg/kg every 18-24 hours 8
1200-2000 grams, >7 days: 7.5-10 mg/kg every 8-12 hours 8

Critical Pitfall: Never use fixed 500 mg doses in pediatrics—this ignores weight entirely and risks treatment failure 8

Renal Impairment Dosing

Fundamental Principle

Do NOT reduce the mg/kg dose in renal impairment—smaller doses compromise the concentration-dependent bactericidal effect and risk treatment failure 2, 9. Instead, extend the dosing interval while maintaining the full mg/kg dose 2, 9.

Dosing Strategy

Maintain 12-15 mg/kg per dose 2, 9
Reduce frequency to 2-3 times weekly (every 2-3 days) 2, 4, 9
This approach preserves peak concentrations while avoiding toxicity through extended intervals 9

Calculation Methods

Method 1: Interval Extension (Preferred)

If serum creatinine is available: New interval (hours) = Serum creatinine (mg/dL) × 9 1
Example: If creatinine = 2 mg/dL, give 7.5 mg/kg every 18 hours 1

Method 2: Dose Reduction at Fixed Intervals

Give loading dose of 7.5 mg/kg initially 1
Maintenance dose = (Observed CrCl / Normal CrCl) × Loading dose, given every 12 hours 1
Alternative rough guide: Divide normal dose by serum creatinine value 1

Hemodialysis Patients

Administer after dialysis to facilitate directly observed therapy and avoid premature drug removal 2, 9
Use 12-15 mg/kg per dose, 2-3 times weekly 2, 4

Therapeutic Drug Monitoring

Target Levels

Once-Daily Dosing:

Peak: 65-80 mg/L (for 3× weekly dosing) or 25-35 mg/L (for daily dosing) 4, 1
Trough: <5 mg/L 4, 9

Divided Dosing:

Peak: 30-40 mg/L (measured 30-90 minutes after infusion) 8, 9
Trough: <10 mg/L (just prior to next dose) 1

Monitoring Schedule

Measure peak levels within the first week of therapy 4
Measure trough levels weekly for 4 weeks, then every 2 weeks when stable 4
Peak concentrations >35 mcg/mL and trough concentrations >10 mcg/mL should be avoided 1

Predictors of Inadequate Levels

Even with 25 mg/kg dosing, 33% of critically ill patients fail to achieve target peak concentrations 7. Risk factors include:

Positive 24-hour fluid balance (OR 1.06 per 250 mL increment) 7
BMI <25 kg/m² when using total body weight for dosing 7
Consider higher doses (>25 mg/kg) in patients with significant fluid overload 7

Obesity Dosing Adjustment

Use ideal body weight + 40% of excess weight for dose calculation 4

Baseline and Ongoing Monitoring

Baseline Assessment

Audiogram, vestibular testing, Romberg testing 2
Serum creatinine measurement 2

Monthly Monitoring

Renal function assessment 2
Question regarding auditory or vestibular symptoms 2
Repeat audiogram and vestibular testing if symptoms of eighth nerve toxicity develop 2

Duration of Therapy

Usual duration: 7-10 days 1
Limit treatment to short-term whenever feasible 1
For complicated infections requiring >10 days: Re-evaluate need and monitor amikacin serum levels, renal, auditory, and vestibular functions closely 1
For complicated intra-abdominal infections: 4-7 days unless source control is difficult 2

Administration

Intravenous infusion over 30-60 minutes for adults 1
May be given intramuscularly 1
Dilute 500 mg vial in 100-200 mL of 0.9% sodium chloride or 5% dextrose 1

Toxicity Profile

Ototoxicity

High-frequency hearing loss occurs in 24% of patients receiving amikacin, with higher rates in those receiving longer treatment and/or higher doses 2
Risk increases with cumulative doses >100-120 grams 2, 9
Amikacin causes less vestibular dysfunction than streptomycin 2
Risk increased with concurrent loop diuretics 2

Nephrotoxicity

Occurs in 8.7% of patients overall, but only 3.4% in patients without risk factors 2
Higher frequency in patients with initially elevated creatinine, larger total doses, and concurrent nephrotoxic agents 2
Amikacin may be more nephrotoxic than streptomycin 2

Contraindications

Pregnancy: Contraindicated due to risk of fetal nephrotoxicity and congenital hearing loss 2, 4

What is the recommended amikacin dosing regimen for adults and children, including loading dose, maintenance dose, renal function adjustment, and therapeutic drug monitoring?

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