Targeting Gentamicin Therapeutic Ranges During the First Week of Life in Infants in Neonatal Intensive Car

Background: The absence of published recommendations for optimum dosing of gentamicin in premature neonates led us to develop dosing schedules for the neonatal population based on post‐conceptional age, and to audit the results periodically. Our previous study results supported the use of a gentamicin loading dose as well as higher maintenance doses at longer dose intervals. However, areas for improvement were identified. Aim: To further refine gentamicin dosing schedules to improve therapeutic range targeting during the first week of life in infants in the Neonatal Intensive Care Unit. Method: A revised gentamicin dosing schedule was formulated and instituted during an 8‐month period in 1999‐2000. All infants > 35 weeks gestation received a loading dose of 5 mg/kg with a maintenance dose of 4 mg/kg (increased from 3.5 mg/kg during a 7‐month period in 1999) every 48 hours for infants >30 weeks gestation, and every 36 hours for those 30‐34 weeks gestation. Infants <34 weeks gestation were given 4 mg/kg every 36 hours without a loading dose. Blood samples for trough concentration measurement were taken immediately before the second dose and those for peak concentration 30 minutes after the completion of the 1‐hour infusion of the second dose. As the majority of the infants received gentamicin shortly after birth, analysis was performed on the data collected during the first few days of life. The results from this dosing schedule were compared with our previous data from 1999. Results: Two hundred and eleven pairs of serum gentamicin peak and trough concentrations in 1999 and 120 pairs in 1999‐2000 were eligible for analysis. The 1999‐2000 gentamicin dosing schedule resulted in 100% of trough and 88.2% of peak concentrations falling within the targeted ranges in infants >30 weeks gestation and 79.5% of trough and 88.6% of peak concentrations falling within the respective targeted ranges in infants <37 weeks gestation. In infants 30‐34 weeks gestation there were similar results for both dosing schedules. Overall, 88.3% of serum gentamicin trough concentrations and 85.8% of peak concentrations were within the targeted ranges during the first postnatal week using the 1999‐2000 schedule. Conclusion: The results of this study suggest improved gentamicin therapeutic concentration targeting using the 1999‐2000 dosing schedule. A larger study is required to confirm the statistical significance of our findings.