Naproxen is frequently used as an anti inflammatory and to add pain relief for instance after surgery. However, there seems to be concern about prescribing it for the breastfeeding mother. I hope this information helps.

pdf of information Naproxen and Breastfeeding factsheet

If it was useful maybe you need to buy the book?

Naproxen is an anti-inflammatory drug used more frequently since concerns were raised about long term cardiovascular risk of diclofenac. It is generally seen as more effective than ibuprofen. Concerns have been raised that its longer half life produces more of a risk to a breastfeeding baby. It is only taken twice a day at 12 hourly intervals.

Naproxen is more than 99% bound to plasma proteins. Davies and Anderson (1997) reported that although naproxen is excreted into breastmilk, the amount of drug transferred comprises only a small fraction of the maternal exposure. Relative infant dose quoted as 3.3% (Hale 2023 online access) lower than 10% regarded as compatible with breastfeeding.

 In Jamali and Stevens’ study (1983) only 0.26% of the mother’s dose was recovered from the infant and adverse effect reports are low.

 The BNF considers that the amount of naproxen distributed into breastmilk is too small to be harmful to a breastfed infant; however, some manufacturers recommend that breastfeeding should be avoided during naproxen therapy, due to licensing considerations rather than potential risk.  

References see Breastfeeding and Medication Text