Evaluation of an amikacin loading dose for nosocomial infections in very low birthweight infants

Aim: To develop a simplified amikacin dosage regimen for nosocomial infections in preterm infants including a loading dose in order to achieve therapeutic Maximum Serum Concentrations early in the course of therapy. Methods: Open, non-comparative study during November 2000 to April 2001. The modified amikacin dosing and monitoring protocol included a loading dose of 10 mg/kg in the first week of life, followed by a maintenance regimen of 7.5 mg/kg every 24 h. After the first week of life the corresponding doses were 17 mg/kg ( loading) and 15 mg/kg ( maintenance). A peak level was measured 30 min after the second dose, a trough level immediately before the third dose. Results: Twenty-five very low birthweight infants ( median birthweight 739 g, median gestational age 25 wk) who had 34 episodes of amikacin treatment were included in the analysis. Median amikacin peak and trough values were 37.1 mumol/l and 6.3 mumol/ l, respectively. Twenty-nine of all peak levels (85%) and 30 of all trough levels (88%) were within the targeted range of > 35 mumol/l and < 8.5 μmol/l, respectively. All patients with elevated trough levels were of extremely low birthweight and were born in the 24th week of gestation. Hearing evaluations were performed in 17 of 19 surviving infants at discharge home, all of which gave normal results. Conclusion: The new amikacin dosing protocol yielded targeted peak and trough concentrations in a high percentage of very low birthweight infants with nosocomial infection after the first week of life. Our simplified dosage regimen achieved acceptable serum concentrations in all birthweight and gestational age groups, with the exception of extremely low birthweight infants weighing less than 700 g and/or with a gestational age of 24 wk or less. Only limited information can be gained from our data regarding the use of amikacin during the first week of life.