What is the maximum dose of amikacin (an aminoglycoside antibiotic) that can be given to an adult patient with normal renal function?

Maximum Amikacin Dosing

For adults with normal renal function, the maximum daily dose of amikacin is 15 mg/kg/day (not to exceed 1.5 grams/day), typically administered as a single daily dose or divided into 7.5 mg/kg every 12 hours or 5 mg/kg every 8 hours. 1, 2

Standard Adult Dosing Parameters

• Weight-based maximum: 15 mg/kg/day is the absolute ceiling for total daily administration by all routes 1, 2
• Absolute maximum: 1.5 grams (1,500 mg) per day regardless of body weight, even in heavier patients 2
• Age adjustment required: Patients over 59 years should receive a reduced maximum of 10 mg/kg/day (750 mg) due to increased risk of ototoxicity and nephrotoxicity 1, 3, 4

Administration Schedules

The 15 mg/kg/day maximum can be administered via three approaches 2:

• Once daily: 15 mg/kg as single dose (preferred for concentration-dependent killing)
• Twice daily: 7.5 mg/kg every 12 hours
• Three times daily: 5 mg/kg every 8 hours

Pediatric Maximum Dosing

• Children and older infants: 15-30 mg/kg/day (maximum 1 gram/day) as single daily dose 1, 3
• Newborns: Loading dose of 10 mg/kg, then 7.5 mg/kg every 12 hours 2

Important caveat: The higher pediatric range (up to 30 mg/kg/day) is reserved for severe infections or special populations like cystic fibrosis patients with altered pharmacokinetics, and requires therapeutic drug monitoring 5

Special Clinical Contexts

Tuberculosis and Drug-Resistant Infections

For mycobacterial infections, the dosing paradigm differs slightly 1:

• Initial intensive phase: 15 mg/kg/day (1 gram maximum) given 5-7 days per week
• Continuation phase: After 2-4 months or culture conversion, reduce frequency to 2-3 times weekly while maintaining the 12-15 mg/kg per dose (not reducing the milligram amount)

Renal Impairment

Critical principle: Never reduce the milligram dose—only extend the dosing interval 1, 3, 4

• Maintain 12-15 mg/kg per dose but administer 2-3 times weekly instead of daily 1
• This preserves concentration-dependent bactericidal activity while preventing accumulation 1
• Administer after hemodialysis to avoid premature drug removal 1, 3

Critically Ill and Septic Patients

Emerging evidence suggests higher loading doses may be necessary in severe sepsis 6, 7:

• Loading doses of 25-30 mg/kg have been studied in septic shock patients to achieve adequate peak concentrations 7
• A 30 mg/kg loading dose achieved target peak levels (>60 mcg/mL) in 76% of critically ill patients without increased nephrotoxicity 7
• However, these exceed FDA-approved maximum dosing and should only be considered with therapeutic drug monitoring in life-threatening infections 7

Therapeutic Drug Monitoring Targets

To ensure the maximum dose is both effective and safe 3, 2:

• Peak levels: 25-35 mcg/mL for daily dosing; 65-80 mcg/mL for three-times-weekly dosing 3
• Trough levels: Must remain <5 mcg/mL to prevent toxicity 3, 2
• Timing: Measure peak 30-90 minutes after infusion; trough immediately before next dose 2
• Peak concentrations above 35 mcg/mL and trough concentrations above 10 mcg/mL should be avoided 2

Duration Limits

• Standard duration: 7-10 days is typical 2
• Extended therapy: If treatment beyond 10 days is necessary, amikacin use must be re-evaluated with mandatory monitoring of serum levels, renal function, and auditory/vestibular function 2
• Bone infections: Up to 6 months may be required for mycobacterial bone infections 1

Toxicity Monitoring Requirements

Baseline assessment before initiating maximum-dose therapy 1, 3:

• Audiogram and vestibular testing
• Romberg testing
• Serum creatinine measurement

Monthly monitoring during therapy 1, 3:

• Renal function assessment
• Questioning about auditory or vestibular symptoms
• Repeat audiogram if any eighth nerve toxicity symptoms develop

Common Pitfalls to Avoid

Do not use fixed 500 mg doses: This ignores body weight entirely and risks both underdosing (treatment failure) and overdosing (toxicity) 3, 5

Do not exceed 1.5 grams/day in standard therapy: Even in patients weighing >100 kg, the absolute maximum remains 1.5 grams unless treating drug-resistant tuberculosis or in research protocols with intensive monitoring 1, 2

Do not reduce the milligram dose in renal failure: This is the most critical error—extend the interval instead to maintain concentration-dependent killing 1, 3

Do not continue beyond 10 days without reassessment: Prolonged therapy dramatically increases ototoxicity risk (1.5-24% depending on duration) and nephrotoxicity risk (8.7% overall) 3, 2

Obesity Adjustment

For obese patients, calculate dose using adjusted body weight 3:

• Formula: Ideal body weight + 40% of excess weight
• This prevents excessive dosing while ensuring adequate tissue penetration

Absolute Contraindication

Pregnancy: Amikacin is absolutely contraindicated due to risk of fetal nephrotoxicity and congenital hearing loss 1, 3