Many different drugs can affect the infant's ability to breastfeed, including their sucking reflex. Drugs can also impact on the mother's ability to lactate.

Evidence of the direct effect, and potential harm, of drugs taken by a breastfeeding mother on her infant is generally limited. It is advisable to prescribe only essential drugs to mothers during breastfeeding. Absence of information under a drug in the BNF does not imply safety. Potential harm can be inferred from:

  1. The amount of drug or active metabolite passed across to the infant (pharmacokinetics of mother & drug distribution in breastmilk.)
  2. Absorption, distribution, and elimination of drug by the infant (infant pharmacokinetics.)
  3. The nature of the effect of the drug on the infant (pharmacodynamic properties of the drug in the infant.)


The BNF states that the amount of most drugs delivered in breastmilk is usually insufficient to cause a discernible effect on the baby. However, professionals should be aware that even a small amount of drug has the possibility of inducing a hypersensitivity reaction in the infant. The BNF identifies drugs that:

  1. Should be used with caution or are contra-indicated in breastfeeding.
  2. Can be given to breastfeeding mothers as the quantity of drug present in breastmilk is too small to be harmful to the infant. 
  3. Might present in breastmilk in significant amount but are not known to be harmful.


Important examples- see questions on this website for more examples.

Phenobarbital: inhibits infant's sucking reflex.

Bromocriptine: affects lactation in mother. The drugs stimulates dopamine receptors in the brain and inhibits the release of prolactin by the pituitary.  

Lithium: present in breastmilk and risk of toxicity in infant.

Oral retinoids: avoid in pregnancy due to teratogenicity so advised to be avoided in breastfeeding.


Anti-cancer drugs

Amiodarone: present in significant amounts in milk. Risk of neonatal hypothyroidism from release of iodine.

Gold salts

Prescribing in breastfeeding: is it safe? 21,22

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