1. ¹Department of Bioengineering, University of Washington, Seattle, Washington, USA
2. ²Department of Obstetrics and Gynecology, University of Washington, Seattle, Washington, USA
3. ³Department of Pharmacy, University of Washington, Seattle, Washington, USA
4. ⁴Division of Clinical Research, Fred Hutchinson Cancer Research Center, University of Washington, Seattle, Washington, USA

Correspondence: MF Hebert, (mhebert@u.washington.edu)

Received 11 December 2006; Accepted 5 January 2007; Published online 28 February 2007.

Abstract

Amoxicillin is recommended for anthrax prevention in pregnancy. The objective of this study was to evaluate the pharmacokinetics of amoxicillin during pregnancy and postpartum (PP). Sixteen women received amoxicillin during gestation (18–22 weeks (T2) and 30–34 weeks (T3)) as well as 3 months postpartum (PP) to evaluate single-dose pharmacokinetics. Amoxicillin compartmental pharmacokinetic parameters were used to simulate amoxicillin concentration–time profiles following different dosage strategies. Amoxicillin CL_renal (T2: 24.86.7 l/h, P<0.001; T3: 24.03.9 l/h, P<0.001; and PP: 15.32.6 l/h) and renal CL_secretion (T2: 280105 ml/min, P<0.002; T3: 25954 ml/min, P<0.001; and PP: 16747 ml/min) were higher during pregnancy than postpartum. Simulations suggest that amoxicillin concentrations adequate to prevent anthrax may be difficult to achieve during pregnancy and postpartum. Increases in amoxicillin CL_renal and renal CL_secretion reflect increases in filtration and secretory transport or diminished reabsorption in the kidneys. Amoxicillin may not be an appropriate antibiotic for post-anthrax exposure prophylaxis.