Antiviral very active against herpes simplex and zoster-varicella.Intravenous, oral and topical (dermatological and ophthalmological) administration.Authorized use in newborns and infants. It is excreted in breast milk in clinically insignificant amounts, much lower than the dose used in newborns and infants (Drake 2012, Bork 1995, Taddio 1994, Don 1991, Meyer 1988, Lau 1987), and no problems have been observed in infants whose mothers were taking acyclovir (Taddio 1994). There is not systemic absorption of topical Acyclovir. List of WHO essential medicines: compatible with breastfeeding (WHO / UNICEF 2002).American Academy of Pediatrics: medication usually compatible with breastfeeding (AAP 2001).