Phenylephrine, an ingredient in pediatric cough and cold preparations, is considered safe. While excretion into breast milk is unknown, it is unlikely to be excreted into breast milk in large quantities due to its poor bioavailability.

Why is phenylephrine bad for breastfeeding?

Phenyephrine is poorly bioavailability (not well absorbed from the gut) so it is not likely to produce effects in a breastfed infant with normal doses. Because of pseudoephedrine's effect on milk production, concerns exist that phenylephrine may suppress milk although there is no evidence that this occurs.

Does phenylephrine reduce milk supply?

Summary of Use during Lactation

The oral bioavailability of phenylephrine is only about 40%,[1] so the drug is unlikely to reach the infant in large amounts. However, intravenous or oral administration of phenylephrine might decrease milk production.