Can amikacin be given as a once-daily dose to an infant with a history of UTI treated with ceftriaxone and amikacin?

Once-Daily Amikacin Dosing in Infants with Previous UTI

Yes, amikacin can be administered as a once-daily dose in this infant with a history of UTI previously treated with ceftriaxone and amikacin. This dosing regimen is supported by current guidelines and evidence demonstrating efficacy and safety.

Recommended Dosing for Infants

For infants with normal renal function, the recommended once-daily dosing of amikacin is:

• 15-22.5 mg/kg IV once daily 1

This is preferable to the traditional multiple daily dosing regimens for several reasons:

Benefits of Once-Daily Dosing

1. Pharmacokinetic Advantages:

   • Higher peak concentrations enhance bacterial killing (concentration-dependent killing)
   • Extended post-antibiotic effect
   • Lower trough levels may reduce toxicity risk

2. Reduced Toxicity Profile:

   • Lower risk of nephrotoxicity and ototoxicity due to lower trough concentrations
   • Studies show once-daily dosing is equally or better tolerated than conventional schedules 2

3. Practical Advantages:

   • Simplified administration schedule
   • Reduced nursing time
   • Fewer venipunctures for the infant

Monitoring Recommendations

When administering once-daily amikacin:

• Therapeutic Drug Monitoring:

  • Measure serum amikacin levels after 72 hours of therapy
  • Target peak concentrations: 30-35 μg/mL (measured 30-90 minutes after injection)
  • Target trough concentrations: <10 μg/mL (measured just before next dose) 3
  • Avoid peak concentrations above 35 μg/mL and trough concentrations above 10 μg/mL

• Renal Function Assessment:

  • Measure baseline serum creatinine before starting therapy
  • Reassess renal function periodically during treatment
  • Consider dose adjustment if renal function changes 3

Special Considerations for This Case

Since this infant has a history of previous amikacin treatment:

1. Review Previous Response:

   • Assess for any previous adverse reactions
   • Check previous therapeutic drug levels if available

2. Renal Function:

   • Ensure normal renal function before initiating therapy
   • Preterm infants have higher risk of toxic amikacin levels (62% vs 21% in term infants) 4

3. Duration of Therapy:

   • For UTIs, typically 7-10 days of therapy is recommended
   • Limit duration to short term whenever feasible 3

Caution

Be aware that preterm infants have immature renal function and may require dose adjustments. Studies have shown that preterm infants have significantly higher median trough levels compared to term infants (11.33 μg/ml vs 8.5 μg/ml) when given the same weight-based dose 4.

If the infant has any signs of renal impairment, consider either:

1. Administering normal doses at prolonged intervals, or
2. Administering reduced doses at fixed intervals

Both approaches should be guided by serum amikacin concentrations and creatinine clearance values 3.