Virtually every drug a mother takes passes into her milk.
Some get through in much higher concentrations than others. Most drugs have such low known risks that breastfeeding is considered safe. However, a few are potentially harmful, either because of known side-effects which affect adults as well, or because they have a different action in a baby, become concentrated in milk, or aren’t broken down by a young baby’s body. Some drugs can cause a sensitivity or allergy which may be dangerous with repeated doses.
Knowledge of how some drugs affect breastfed babies is far from complete because of the difficulty in doing trials in breastfeeding mothers. It is clearly unacceptable to give healthy women drugs to see what happens to their babies. And the numbers of breastfeeding women who need any but the most common of drugs is very small. There’s also the very real difficulty of measuring drug levels in milk.
Ideally, a breastfeeding mother should not take any drugs, medical or recreational. However, this is obviously the ideal advice and sometimes a drug is essential, even life-saving. If it happens to be dangerous for her baby, she'll have to wean, even if only temporarily. If any one drug isn’t safe for a breastfed baby, there’s often an alternative that is.
If you need any drug while breastfeeding, first remind your doctor that you are breastfeeding so he or she can check the safety of the drug to your baby if necessary.
Babies born pre-term or small for dates, or who have jaundice or a liver or kidney problem, a family history of allergy, or a deficiency of the enzyme G6PD, may be particularly susceptible to the adverse effects of certain drugs. Your doctor should be able to find out easily which drugs are unsafe or better avoided by a breastfeeding mother.
Dr. Penny Stanway
June 2009
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Breastfeeding Twins
