Prednisolone
CASRN: 50-24-8
For other data, click on the Table of Contents
Drug Levels and Effects:
Summary of Use during Lactation:
Limited information indicates that maternal doses of prednisolone up to 50 mg produce low levels in milk and would not be expected to cause any adverse effects in breastfed infants. With high maternal doses, avoiding breastfeeding for 4 hours after a dose should markedly decrease the dose received by the infant. However, this maneuver is probably not necessary in most cases.
Acyclovir
CASRN: 59277-89-3
For other data, click on the Table of Contents
Drug Levels and Effects:
Summary of Use during Lactation:
Even with the highest maternal dosages, the dosage of acyclovir in milk is only about 1% of a typical infant dosage and would not be expected to cause any adverse effects in breastfed infants. No special precautions are required
These are the summaries from an American website toxnet.nlm.nih.gov/cgi-bin/sis/search for both meds.
I would have used this source (along with others) if I had been asked for info. Obviously it is difficult for me to comment on your case without having all clinical details. but bear in mind your son is 7 months old and therefore his ability to metabolise meds is much better than a newborn and your milk is not his sole source of nutrition.
It is a shame it is the weekend otherwise I would have suggested phoning the pharmacy dept and asking again.