Breastfeeding definitions

Excretion into milk

This provides general information on the extent of excretion of the medicine into the breast milk.

Milk to plasma ratio

The milk to plasma ratio is a numerical value (expressed as a single number or range) for a measure of the amount of medicine excreted into breast milk. This value represents the concentration of medicine in the milk relative to the maternal plasma level. This is of particular use when maternal plasma concentrations can be directly measured or estimated.

Relative infant dose

The relative infant dose is a calculation that divides the dose offered to the infant via milk (mg/kg/dose) by the mother’s weight-adjusted dose (mg/kg/dose). This weight-normalising method indicates approximately how much of the “maternal dose” the infant is receiving.  An infant dose via breast milk of less than 10% of the maternal weight-adjusted dose is generally considered safe in breastfeeding.

Breastfeeding summary

General information regarding the use of the medicine during breastfeeding, based on a combination of available literature review. Alternative treatment options and possible monitoring parameters may also be included if applicable. 

Last Updated: 5 February 2015

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Practical recommendations

The Therapeutic Goods Administration (TGA) pregnancy categories and manufacturer’s product information are sometimes difficult to interpret. The Women’s PBMG has developed a series of practical recommendations for medicines used during pregnancy and breastfeeding.