There are no known publications on the influence of penciclovir during breastfeeding, although it seems unlikely that the topical application of this substance in the mother can cause disorders in the baby, except for the area located on suction.
Warning of the manufacturer:
Studies in rats show that penciclovir is excreted in the breast milk of the female rats that were given famciclovir (famciclovir is the oral form of penciclovir; this drug is converted in vivo into penciclovir). There is not information available about the elimination of penciclovir through human milk.
Since the penciclovir safety in pregnant women has not been established, this medication should be used during pregnancy or while breastfeeding when the doctor recommends and whether the potential benefits are considered to outweigh the risk associated with treatment.