Oseltamivir and zanamivir can be used during breastfeeding when clinically indicated. Recommendations apply to full term, healthy infants only.

General considerations

It is important to complete an individual risk assessment for your patient and to apply the principles of prescribing in breastfeeding when looking at the available information and making treatment decisions.


Oseltamivir and zanamivir are used for the prevention and treatment of influenza.

Limited data suggest that oseltamivir passes into breastmilk in negligible amounts. It is the preferred antiviral for use during breastfeeding.

There is no published evidence for the use of zanamivir in breastfeeding, however infant exposure is expected to be insignificant. Zanamivir can be used by any route during breastfeeding when indicated.

Clinical considerations

Treatment choice should be based on the clinical scenario with safety in breastfeeding a secondary consideration.

If the breastfed infant also needs direct treatment or prevention for influenza, the recommended dose of oseltamivir or zanamivir for infants should be given directly to the infant. This is regardless of whether they are also exposed to oseltamivir or zanamivir via breast milk.

Breastfeeding with influenza infection

Breastfeeding should continue as normal.

There is no evidence that influenza can be transmitted via breast milk. Breast milk contains antibodies and other bioactive factors which can help protect the infant from influenza.

Minimising risk of infant infection through close contact

In order for breastfeeding to be facilitated it is important that mother and baby stay close together. However, consider the following to reduce the risk of the infant becoming infected:

  • Wash hands for at least 20 seconds before touching the infant or any expressing equipment.
  • Avoid coughing or sneezing on the infant while breastfeeding.
  • If used, clean breast pumps as recommended by the manufacturer after each use.

Specific recommendations

Patient Information

The NHS website provides advice for patients on the use of specific medicines in breastfeeding.

Contact us

Get in touch with the UK Drugs In Lactation Advisory Service (UKDILAS), our specialist breastfeeding medicines advice service if you need support in the following situations:

  • you need further advice
  • the medicine in question is not included here
  • the infant is unwell or premature
  • multiple medicines are being taken

About our recommendations

Recommendations are based on published evidence where available. However, evidence is generally very poor and limited, and can require professional interpretation. Assessments are often based on reviewing case reports which can be conflicting and lack detail.

If there is no published clinical evidence, assessments are based on: pharmacodynamic and pharmacokinetic principles, extrapolation from similar drugs, risk assessment of normal clinical use, expert advice, and unpublished data. Simulated data is now increasingly being used due to the ethical difficulties around gathering good quality evidence in this area.


Full referencing is available on request.

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