Background: Appropriate dosing of gentamicin in critically ill neonates is still debated.
Objective: To assess the peak concentration (Cmax) and area-under-the-time-concentration curve (AUC0-24) of
gentamicin and to simulate the recommended doses using the Monte Carlo method.
Methods: This was a retrospective study on critically ill neonates carried over a one-year period. The demographic
characteristics, dosage regimen and gentamicin concentrations were recorded for each neonate. Using Bayesian
pharmacokinetic modeling, Cmax and AUC0-24 were predicted. Dose recommendations for the target Cmax (μg/ml) of
12 were obtained, and Monte Carlo simulation (100,000 iterations) was used for predicting the pharmacokinetic
parameters and recommended doses for various birth weight categories.
Results: Eighty-two critically ill neonates (with an average gestational age of 33.7 weeks; and birth weight of 2.1 kg)
were recruited. Higher Cmax and AUC0-24 values were predicted in premature neonates, with greater cumulative AUCs
in extremely preterm neonates. The average administered dose was 4 mg/kg/day and 75% of the participants had Cmax
greater than 12 μg/ml following a single dose, and 85% were found to be at steady state. On the contrary, only 25%
of the study population had the recommended AUC0-24 (above 125 μg-hr/ml). Simulation tests indicate that 90% of
the critically ill neonates would achieve recommended Cmax with doses ranging between 5 and 6 mg/kg/day.
Conclusion: Currently used dose of 4 mg/kg/day is adequate to maintain Cmax in a large majority of the study
population, with one-fourth population reporting the recommended AUC0-24. Increasing the dose to 5-6 mg/kg/day
will more likely help to achieve both the recommended Cmax and AUC0-24 values.