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