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Therapeutic amoxicillin levels achieved with oral administration in term neonates

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The standard treatment of neonatal group B Streptococcus infection is intravenous amoxicillin for 10 days. We investigated whether effective serum amoxicillin concentrations could be reached by switching to oral amoxicillin after 48 h of intravenous administration in full-term neonates with group B Streptococcus infection.


Over 2 years, we included 222 full-term neonates who had early onset group B streptococcal disease responsive to 48 h of intravenous amoxicillin, at which point they were asymptomatic and fed orally. They were switched to oral amoxicillin (300 or 200 mg/kg per day in four divided doses). Steady-state serum amoxicillin concentrations were determined 48 h later by high-performance liquid chromatography; values ≥5 mg/l were considered effective.


Mean gestational age was 39.32 ± 1.5 weeks ,and mean birth weight was 3,422 ± 533 g; 29 newborns were bacteremic. Median serum amoxicillin concentration on oral therapy was 31,.15 (range 11–118) and 25.80 (range 5–84.8) with 300 and 200 mg/kg per day, respectively. None of the infants had a concentration <5 mg/l (p < 0.001). Gastrointestinal tolerance was satisfactory; 216 patients were discharged at 5 days of age, and none was readmitted within the 3-month follow-up.


Early switching to the oral route in asymptomatic full-term newborns with early onset group B streptococcal disease maintained serum amoxicillin concentrations within our predefined therapeutic range (error risk<0.001). This strategy may hold potential for reducing treatment invasiveness and shortening hospital length of stay.

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Correspondence to Christele Gras-Le Guen.

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Gras-Le Guen, C., Boscher, C., Godon, N. et al. Therapeutic amoxicillin levels achieved with oral administration in term neonates. Eur J Clin Pharmacol 63, 657–662 (2007).

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