The full, clinically endorsed recommendation should be obtained from Lareb. 

Rationale for drug selection 

Amoxicillin, alone or with clavulanic acid (ACA), is widely used in pregnancy for the treatment of infections or as antibiotic prophylaxis. Pregnancy-induced changes in amoxicillin pharmacokinetics may necessitate dose adjustments to maintain effective drug concentrations and prevent severe maternal infections that could lead to obstetric complications.

Pharmacokinetics of amoxicillin in pregnancy

Both renal clearance and the volume of distribution are increased in pregnancy, leading to lower amoxicillin concentrations in the blood of pregnant patients compared with non-pregnant adults. Both pharmacokinetic studies and PBPK modelling show that amoxicillin concentrations are reduced by 15-25% during the second and third trimester. The placental transfer of amoxicillin seems to vary between patients. Based on placental-perfusion experiments, the placental transfer of amoxicillin is approximately 30%.  During pregnancy, lower amoxicillin doses are often prescribed. However, the therapeutic range is well-defined based on the pathogen, and pregnancy reduces amoxicillin exposure. To avoid concentrations falling below the therapeutic range, doses similar to those used in non-pregnant adults may therefore be more appropriate. Maternal PBPK models provided evidence on the influence of gestational age on the pharmacokinetics changes of amoxicillin in pregnancy and supported decision-making.

Benefits and risks with the proposed dose adjustments

The expected benefits and associated risk of aligning doses during pregnancy to non-pregnant adults.

In short 

Amoxicillin is given to treat infections during pregnancy. Pregnancy increases clearance and lowers exposure levels. Therefore, it is not justified that during pregnancy lower doses are prescribed than their nonpregnant individuals, and thus aligning these doses may be needed. Based on the weighing of benefits and risks, the working committee derived an appropriate dose adjustments. Consult Lareb for the model-informed dosing recommendations.