What is the recommended dose of amikacin (an aminoglycoside antibiotic) for a 37-day-old infant?

Amikacin Dosing for a 37-Day-Old Infant

For a 37-day-old infant, the recommended dose of amikacin is 15 mg/kg/dose IV every 24 hours. 1

Dosing Rationale

The appropriate amikacin dosing for infants depends on several factors including gestational age, postnatal age, and weight. For a 37-day-old infant, the following considerations apply:

Age-Based Dosing

• According to the Journal of Microbiology, Immunology and Infection guidelines, for neonates with gestational age >34 weeks and postnatal age >7 days (which applies to a 37-day-old infant), the recommended dose is 18 mg/kg/dose IV every 24 hours 1
• However, the more conservative approach of 15 mg/kg/dose IV every 24 hours is generally preferred to minimize toxicity risks while maintaining efficacy 2

Administration Method

• Amikacin should be administered intravenously, infused over 30 minutes
• For infants, intramuscular administration is an alternative but may cause more pain and variable absorption

Monitoring Requirements

Therapeutic drug monitoring is essential to ensure efficacy while avoiding toxicity:

• Peak serum levels: Should be measured 30-90 minutes after infusion

  • Target: 25-35 μg/mL
  • Levels above 35 μg/mL should be avoided 3

• Trough serum levels: Should be measured just before the next dose

  • Target: <10 μg/mL
  • Levels above 10 μg/mL are associated with increased risk of ototoxicity 4

• Renal function: Monitor serum creatinine regularly during therapy

  • Baseline measurement before starting therapy
  • Follow-up measurements every 2-3 days during treatment

Duration of Therapy

• Standard duration is typically 7-10 days 3
• Limit duration to short-term whenever feasible
• For complicated infections where treatment beyond 10 days is considered, re-evaluate the use of amikacin and monitor serum levels and renal/auditory/vestibular functions more closely 3

Toxicity Considerations

Amikacin has potential for significant toxicity in infants:

• Ototoxicity: Risk increases with:

  • Trough concentrations ≥10 μg/mL 4
  • Prolonged treatment courses
  • Higher total cumulative doses

• Nephrotoxicity: Monitor for:

  • Elevated serum creatinine
  • Decreased urine output
  • Electrolyte abnormalities

Important Caveats

• Research has shown that currently recommended dosages may produce excessive serum levels, particularly in very low birth weight infants 5
• Dosing should be adjusted based on therapeutic drug monitoring results
• If the infant has impaired renal function, dosage adjustment is necessary
• Consider alternative antibiotics if prolonged therapy is anticipated or if the infant has pre-existing hearing or renal impairment

Clinical Response Assessment

• Uncomplicated infections due to amikacin-sensitive organisms should respond within 24-48 hours
• If definite clinical response does not occur within 3-5 days, therapy should be reconsidered 3
• Treatment failure may be due to antimicrobial resistance or inadequate source control

Remember that therapeutic drug monitoring is crucial in optimizing amikacin therapy in infants to ensure adequate antimicrobial coverage while minimizing the risk of toxicity.