Breast Milk - Passing of Unwanted Substances

Passing of Unwanted Substances

Despite the risk of substances transmitting from the mother to the child through breast milk, breastfeeding has far more advantages than infant formulas, and, with few exceptions, the WHO recommends exclusive breastfeeding for the first 6 months of life.

The milk-producing cells are most permeable to drugs during the first postpartum week.

Drug characteristics that increase excretion in milk include:

1. Not plasma protein binding
2. Non-ionized
3. Low molecular weight
4. Lipid solubility rather than water solubility
5. Weakly alkaline rather than weak acid

Drugs are transferred from blood plasma across ductal cells to the milk by diffusion or active transport. The latter may result in higher concentration of the drug in the breast milk than in the plasma of the mother.

The amounts of most drugs in milk do not exceed 2% of the total ingested dose.