Oseltamivir or zanamivir – can they be used in breastfeeding mothers for the treatment or prophylaxis of influenza?

Vanessa Chapman, Associate Professional Lead for Medicines Information, Midlands & East, Midlands and East Medicines Advice Service (Midlands site) & UK Drugs in Lactation Advisory ServicePublished

This updated Medicines Q&A evaluates the available evidence for oseltamivir and zanamivir when used in breastfeeding mothers for the treatment or prophylaxis of influenza.

In summary:

  • Both oseltamivir and zanamivir are considered acceptable for use in breastfeeding mothers.
  • The benefits of breastfeeding are considered to outweigh any, albeit unidentified, risks. Use of either drug is not a reason to discontinue, or put limitations on breastfeeding.
  • Oseltamivir and its active metabolite, oseltamivir carboxylate, are excreted into human breast milk in very small amounts. Limited data suggest that clinical sequelae from maternal use would not be expected in a breastfed infant.
  • There are no data on zanamivir use during lactation but based on limited oral bioavailability the systemic exposure of a breastfed infant from maternal treatment, via any route, is expected to be insignificant.
  • If the mother is receiving oseltamivir or zanamivir and the breastfed infant also needs direct treatment or prophylaxis, the recommended dose of oseltamivir or zanamivir for infants should be given to the infant.
  • The UK Drugs in Lactation Advisory Service (UKDILAS) advises that, as a precaution, infants should be monitored for vomiting or diarrhoea.
  • This guidance applies to infants born full term and healthy. If an infant is unwell, premature, or the mother is taking multiple medicines, then an individual risk assessment will need to be made.