To      : Cindy Hirsch
Re      : Topical Metrogel for acne

The topical Metrogel used for acne is basically the same as the MetroGel used
for vaginal application.  As such following the topical application of 1 gm of
topical metronidazole to the face (7.5 mg metronidazole base),  the maximum
serum concentration was 66 ng/ml in only one of ten patients.  This
concentration is 100 times less than the concentration achieved following the
oral ingestion of one single 250 mg tablet.   Three of the above patients had
NO detectible levels at all.  Further, when used vaginally, Metrogel is
also poorly bioavailable in the patient.

Therefore, it is apparent that the topical application provides only
exceedingly low plasma levels in the mother and hence minimal levels in the
breast milk as well.  Further, many individuals mistakenly believe that the
skin of an infant is more permeable than that of an adult.  This is not true,
they just have a higher skin to body mass ratio than adults.  It is unlikely
that the small amounts of Metrogel transferred from mom to infant (via
touching) would be clinically relevant,  or that the bioavailability of such
metronidazole would be sufficient to produce problems in an exposed infant.

Regards

Tom Hale, Ph.D.
Associate Professor of Pediatrics