Amikacin Adult Dosing
For adults with normal renal function, administer amikacin 15 mg/kg/day (maximum 1 gram/day) as a single daily dose, with dose reduction to 10 mg/kg/day (maximum 750 mg) for patients over 59 years of age. 1, 2
Standard Dosing Regimen
Normal Renal Function
- 15 mg/kg/day administered as a single daily dose (preferred) or divided into 7.5 mg/kg every 12 hours or 5 mg/kg every 8 hours 1, 2
- Maximum daily dose should not exceed 1 gram regardless of weight 1, 2
- Once-daily dosing is superior to divided dosing, achieving 83% clinical cure versus 66% with twice-daily dosing, with less nephrotoxicity (21% vs 35%) 3
Age-Related Adjustments
- Patients >59 years: Reduce dose to 10 mg/kg/day (750 mg maximum) due to increased risk of ototoxicity and nephrotoxicity 1, 4, 5
- This age-based reduction is critical and should not be overlooked 6
Obesity Adjustments
- Calculate dose using ideal body weight + 40% of excess weight 5, 6
- Do not use actual body weight in obese patients as this leads to excessive dosing and toxicity 6
Renal Impairment Dosing
Critical principle: Maintain the mg/kg dose at 12-15 mg/kg but reduce frequency—never reduce the individual dose amount. 1, 5, 6
- Reduce dosing frequency to 2-3 times per week while keeping each dose at 12-15 mg/kg 1, 5
- This maintains concentration-dependent bactericidal activity while preventing accumulation 1, 6
- For hemodialysis patients, administer after dialysis to prevent premature drug removal 5, 6
Duration and Frequency Adjustments
- Initial phase: Daily dosing (5-7 days/week) for first 2-4 months 1, 4
- Continuation phase: After culture conversion, reduce to 2-3 times weekly 1, 4
- Typical treatment duration: 7-10 days for most infections 2
- Treatment beyond 10 days requires reassessment with mandatory serum level monitoring 2
Target Serum Concentrations
Peak Levels (30-90 minutes post-infusion)
- Daily dosing: 25-35 mg/L 5, 6
- Three times weekly dosing: 65-80 mg/L 5, 6
- Avoid peaks >35 mg/L with daily dosing to prevent toxicity 2
Trough Levels (immediately before next dose)
- Target: <5 mg/L 5, 6
- Avoid troughs >10 mg/L to prevent nephrotoxicity and ototoxicity 2
- Trough levels correlate with treatment efficacy in renal impairment 7
Monitoring Requirements
Baseline Assessment
Ongoing Monitoring
- Serum levels: Peak within first week, trough weekly for 4 weeks, then every 2 weeks when stable 5
- Renal function: Monthly assessment with questioning about auditory/vestibular symptoms 1, 4, 6
- Repeat audiogram: If any symptoms of eighth nerve toxicity develop 1, 4, 6
Special Clinical Contexts
Uncomplicated UTI
- May use reduced dose of 250 mg twice daily 2
Tuberculosis
- Standard 15 mg/kg/day initially, reducing frequency after 2-4 months or culture conversion 1, 4
- Poor CNS penetration even with meningitis may necessitate higher systemic doses 4, 6
Plague Treatment (Alternative Agent)
- 15-20 mg/kg every 24 hours IV or IM 1
Toxicity Profile
Nephrotoxicity
- Occurs in 8.7% overall, but only 3.4% in patients without risk factors 6
- Higher risk with concurrent nephrotoxic agents, pre-existing renal impairment, and higher cumulative doses 1
Ototoxicity
- High-frequency hearing loss occurs in 1.5-24% of patients 6
- Higher rates with longer treatment duration, higher doses, and concurrent loop diuretics 1, 4
- Amikacin causes primarily cochlear toxicity with less vestibular dysfunction than streptomycin 1
Absolute Contraindications
Critical Pitfalls to Avoid
- Never reduce the mg/kg dose in renal impairment—extend the interval instead 6
- Never use fixed 500 mg doses regardless of weight—this risks underdosing and treatment failure 6
- Never continue beyond 10 days without reassessing drug levels and toxicity monitoring 6, 2
- Never use actual body weight in obese patients—use adjusted body weight formula 5, 6