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Phenylephrine in Breast Milk

author image Kate Harris
Kate Harris has been writing and editing various media types for over 12 years and has been published in several newspapers including the "Linden Herald," "Kuna-Melba News," "Idaho Statesman" and "Copper Herald." She graduated college in 2001 with honors while earning a Bachelor of Science degree in biology and a minor in chemistry.
Phenylephrine in Breast Milk
A baby is drinking milk from a bottle. Photo Credit Pawel_Czaja/iStock/Getty Images

Some prescription and over-the-counter medications used while breast-feeding can cause negative and potentially harmful side effects to a nursing infant. Medications can also diminish a nursing mother’s milk supply. Before taking any prescription or over-the-counter medication, it is essential to consult with a physician to ensure its safe use while breast-feeding.


Phenylephrine is used in over-the-counter medications intended to treat nasal congestion. It acts as a vasoconstrictor, which explains its efficacy as a nasal decongestant because it causes nasal passages to constrict. Only 40 percent of phenylephrine taken orally becomes bioavailable, or useable, within the human body.

Infant Exposure and Effects

Since the bioavailability of this drug is limited when administered orally, it is unlikely to be present in large amounts in breast milk. According to the Drug and Lactation Database published by the National Institutes of Health, no relevant data is available to indicate maternal or infant drug levels or infant effects after phenylephrine use during breast-feeding.

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Lactation Effects

Although it is unknown whether phenylephrine passes directly into breast milk, it is possible that it can decrease milk production. Another commonly used decongestant, pseudoephedrine, has been shown to reduce milk supply by more than 20 percent. Pseudoephedrine is close in structure and mechanism of action to phenylephrine. Use phenylephrine with caution if you're a mother who does not have a well-established milk supply.


In order to decrease the potential effects of phenylephrine on the nursing infant, nasal sprays or ophthalmic drops are alternatives that are less likely to cause unwanted side-effects. The American Academy of Pediatrics suggests that lactating women consider whether the medication is necessary, and ensure selection of the safest drug available. Taking the medication after nursing the infant can decrease the infant’s drug exposure.

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