It should not be a problem for the dog that is nursing. It could be an issue for the one that is pregnant as it can cause birth defects.
This is called a teratogenic medication which means it can cause varied defects in embryos.
The defects can be varied based on which part of the fetus is impacted by the chemical changes from the drug.
I'm sure you've stopped using it and you should be aware the other meds you might use are also an issue such as albon.
But you might be reassured that there are studies out there showing there is no relationship between using this med and birth defects in humans
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9278206&dopt=Abstract
http://www.motherisk.org/prof/updatesDetail.jsp?content_id=328
Some of the cites on this drug say that its teratogenic in *some* species but does not specifically list the dog as one of them.
You will have to wait and see and I'd have the vet examine the pups carefully before selling them.
Hope this helps you!
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