Although paracetamol is considered safe for use during breastfeeding, it is not known if phenylephrine passes into breast milk, or its effect on a nursing infant. As a result, this medicine should not be used by breastfeeding mothers, unless your doctor considers the expected benefit is greater than any possible risk to the nursing baby. Seek medical advice from your doctor before taking this medicine if you are breastfeeding.
phenylephrine is the other active ingredient which causes the blood vessels in the nose to contract.
So not helpful really but just that the effects are not known. I don't suppose it's that strong though being over-the-counter.
I did this and dd was fine. SHe was wakeful and agitated most of the time anyway so I didn't notice any difference (and at least I didn't have a blocked up nose to deal with at the same time). I phoned NHS direct and they said a one off was no problem, but that was 3 yrs ago and ingredients change. I'd give them a ring just to make yourself feel better.
Well we're both still alive and well this morning, so it seems I haven't damaged my child. Or at least not in any obvious way - he'll probably turn out to be a psychopath now, all down to that one Lemsip Max....