I have been informed that this drug does not have much advantage over
acyclovir, and Dr. Hale mentions this as well.  As usual, someone used
the newer drug when the older one would probably have done just as
well.

If the mother is getting only one dose, I don't think there is an
issue.  Is this the way it is given?

Just because the M:P is greater than 1 does not mean there is a big
problem.  Even if there is some concentration of drug in the milk, low
plasma levels are the rule, and concentration of a small amount does
not mean much.  The oral availability of the drug is fairly low, but
higher than acyclovir.

Jack Newman, MD, FRCPC