What is the recommended dose of Amikacin (generic name) for a patient?

Amikacin Dosing Recommendations

Standard Adult Dosing

For adults with normal renal function, administer amikacin 15 mg/kg/day (maximum 1 gram/day) as a single daily dose, given intramuscularly or intravenously over 30-60 minutes. 1

This dosing can alternatively be divided into 7.5 mg/kg every 12 hours or 5 mg/kg every 8 hours, though once-daily dosing is preferred for its concentration-dependent bactericidal effect and comparable safety profile. 1, 2

Age-Adjusted Dosing

For patients over 59 years of age, reduce the dose to 10 mg/kg/day (maximum 750 mg/day). 3

This reduction is critical because elderly patients have increased risk of both ototoxicity and nephrotoxicity due to age-related changes in renal function and drug clearance. 3

Pediatric Dosing

• Children and older infants: 15-30 mg/kg/day (maximum 1 gram/day) as a single daily dose 3
• Newborns: Loading dose of 10 mg/kg, followed by 7.5 mg/kg every 12 hours 1
• Infants should receive infusions over 1-2 hours 1

Renal Impairment Dosing

In patients with renal insufficiency, maintain the dose at 12-15 mg/kg but reduce the frequency to 2-3 times per week rather than lowering the milligram dose. 3

This approach preserves the concentration-dependent killing effect of amikacin while reducing cumulative toxicity. 3

Practical Adjustment Methods:

• If creatinine clearance is unavailable: Multiply the patient's serum creatinine (mg/dL) by 9 to determine the dosing interval in hours 1

  • Example: Serum creatinine 2.0 mg/dL = dose every 18 hours

• For hemodialysis patients: Administer the dose after dialysis to facilitate directly observed therapy and avoid premature drug removal 3

• Fixed-interval dosing with renal impairment: Give a normal loading dose (7.5 mg/kg), then reduce maintenance doses proportionally based on creatinine clearance 1

Duration and Frequency Adjustments

• Initial phase: 5-7 days per week for the first 2-4 months or until culture conversion 3
• Continuation phase: Reduce to 2-3 times weekly after initial response, depending on efficacy of companion drugs 3
• Typical treatment duration: 7-10 days for most infections 1
• Extended therapy beyond 10 days requires re-evaluation and intensified monitoring 1

Therapeutic Drug Monitoring

Target peak levels are 25-35 mg/L for daily dosing or 65-80 mg/L for three-times-weekly dosing; target trough levels should be <5 mg/L to prevent toxicity. 4, 5

Monitoring Schedule:

• Measure peak levels within the first week of therapy 4, 5
• Measure trough levels weekly for 4 weeks, then every 2 weeks when stable 4, 5
• Baseline assessment: Audiogram, vestibular testing, Romberg testing, and serum creatinine 3
• Monthly monitoring: Renal function assessment and questioning about auditory/vestibular symptoms 3

Critical Safety Considerations

Contraindications:

• Amikacin is absolutely contraindicated in pregnancy due to risk of fetal nephrotoxicity and congenital hearing loss 3

Major Toxicities:

Nephrotoxicity:

• Occurs in 8.7% of patients overall, but only 3.4% in those without risk factors 3
• Higher risk with pre-existing renal impairment, higher cumulative doses, and concurrent nephrotoxic agents 3
• Amikacin may be more nephrotoxic than streptomycin 3

Ototoxicity:

• High-frequency hearing loss occurs in 1.5-24% of patients, with higher rates in longer treatment courses and higher doses 3
• Amikacin causes less vestibular dysfunction than streptomycin 3
• Risk increases with age, concurrent loop diuretics, and cumulative doses above 100-120 grams 3
• Repeat audiogram and vestibular testing if any symptoms of eighth nerve toxicity develop 3

Special Clinical Contexts

Uncomplicated Urinary Tract Infections:

• A reduced dose of 250 mg twice daily may be used 1

CNS Infections:

• Amikacin has poor CSF penetration even with meningitis, which may necessitate higher systemic doses 3, 6

Obese Patients:

• Adjust dose using ideal body weight plus 40% of excess weight 4

Common Pitfalls to Avoid

• Do not use fixed 500 mg doses regardless of weight—this risks underdosing and treatment failure 5
• Do not reduce the milligram dose in renal impairment; instead extend the dosing interval 3
• Do not physically premix amikacin with other drugs; administer separately 1
• Do not continue therapy beyond 10 days without reassessing drug levels and monitoring for toxicity 1
• Failure to respond within 3-5 days requires stopping therapy and rechecking antibiotic susceptibility 1