Serum concentrations of amoxicillin in neonates during continuous intravenous infusion.

Amoxicillin is commonly used for the treatment of neonatal bacterial infection with intermittent dosing (ID) regimens. However, increasing bacterial resistance, in addition to a lack of new antimicrobial agents, urges the optimization of current therapeutic options. Clinical studies in adults suggest continuous infusion (CI) regimens of beta-lactam antibiotics to be superior to ID. There are as yet no guidelines concerning the CI dosing of amoxicillin. The present study was developed to describe the CI pharmacokinetics and -dynamics of amoxicillin during the first 3 days of life in search of the optimal dosing regimen. Neonates with a gestational age above 34 weeks, at risk of neonatal infection and requiring amoxicillin therapy, were included. Serum concentrations of amoxicillin were measured during CI on days 1 and 3 in the steady state. Twenty-two serum samples of 11 patients were collected. All patients reached and retained serum concentrations of amoxicillin within the therapeutic range without exceeding the toxic concentration (serum concentrations on day 1 mean 55.4 mg/l, range 30.9-69.5, SD 10.5, and on day 3 48.8 mg/l, range 25.5-92.4, SD 18.4). There was no significant decrease in concentration from day 1 to day 3 (p = 0.38). This study showed therapeutic, nontoxic concentrations of amoxicillin in neonates on CI of amoxicillin in the first 3 days of life. Randomized controlled trials should reveal whether the clinical benefits of the CI of amoxicillin exceed those of ID regimens.