Hello,
Regarding Benylin extra potent, the ingredients may vary depending on the type (Cough, congestion, All in one etc.)
But if we look at ingredient by ingredient:
Dextrometorphan (DM), for dry cough: short term safe.
Pseudoephedrine, decongestant: safe, discontinue use if after a few days you observe a change in milk production or irritability of the baby.
Guaifenesin (expectorant): safe
Acetaminophen: safe
Chlorpheniramine, antihistamine: safe, discontinue use if after a few days you observe a change in milk production or drowsiness in the baby.
In short, all the ingredients are safe as long as the prescribed dose is respected and on a short term basis.
I hope I have answered your question.