Therapeutic amoxicillin levels achieved with oral administration in term neonates

Eur J Clin Pharmacol. 2007 Jul;63(7):657-62. doi: 10.1007/s00228-007-0307-3. Epub 2007 May 12.


Aims: 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.

Methods: 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 > or =5 mg/l were considered effective.

Results: 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.

Conclusion: 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.

Publication types

  • Clinical Trial

MeSH terms

  • Administration, Oral
  • Amoxicillin / administration & dosage*
  • Amoxicillin / blood*
  • Amoxicillin / therapeutic use
  • Anti-Bacterial Agents / administration & dosage*
  • Anti-Bacterial Agents / blood*
  • Anti-Bacterial Agents / therapeutic use
  • Chromatography, High Pressure Liquid
  • Drug Administration Schedule
  • Female
  • Humans
  • Infant, Newborn
  • Intensive Care Units, Neonatal
  • Male
  • Streptococcal Infections / drug therapy
  • Streptococcus agalactiae


  • Anti-Bacterial Agents
  • Amoxicillin