Gentamicin and tobramycin in neonates: comparison of a new extended dosing interval regimen with a traditional multiple daily dosing regimen.

Because of a lack of data supporting traditional dosing regimens for aminoglycosides, especially in extremely low-birth-weight infants, the authors developed revised dosing guidelines. The new guidelines increased doses to 5 mg/kg (over traditional doses of 2.5 mg/kg) and lengthened the dosing interval. When results of the two regimens were compared in 120 infants, 26.8% of infants in the traditional dosing group had subtherapeutic levels at <5 microg/mL, whereas only 1.3% of infants in the new practice dosing group were subtherapeutic. With the new dosing practice, serum levels in 1.3% of infants also exceeded the upper therapeutic range of 12 microg/mL. In conclusion, by increasing the dose of aminoglycosides and extending the dosing intervals, therapeutic levels-as defined by a C min <2 microg/mL and a C max of 5 to 12 microg/mL--were obtained significantly more often. In essence the regimen involves once daily dosing for infants <1200 g who are >30 days of age and for infants <1200 g who are >7 days of age. Serum concentrations still need to be monitored where clinically indicated.