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.
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.
Oseltamivir is the preferred choice during breastfeeding. Infant monitoring is still required.
As a precaution, infants should be monitored for vomiting, diarrhoea, irritability, and changes in sleep.
Limited evidence indicates that oseltamivir and its active metabolite pass into breastmilk in negligible amounts.
The active metabolite also has poor oral bioavailability, limiting the amount the infant can absorb from breast milk. Therefore, infant side effects from exposure via breastmilk would not be expected.
Oseltamivir is used therapeutically in children from birth (unlicensed); the doses used are far greater than the amounts reported in breast milk.
Use with caution
Zanamivir, either by inhalation or intravenously, can be used with caution during breastfeeding. Infant monitoring is required.
As a precaution, infants should be monitored for vomiting and skin reactions.
There is no published evidence of use during breastfeeding. However, the amount expected to pass through into the breast milk is unlikely to cause any side effects in a breastfed infant.
Maternal systemic absorption after inhalation of zanamivir is low, therefore the amount available to pass into breast milk will be minimal.
Intravenous administration will result in higher maternal serum concentrations. However, since zanamivir has very poor oral bioavailability, this limits the amount the infant can absorb from the breast milk.
Zanamivir also has a relatively short half-life (2–5 hours), and therefore accumulation and side effects in the infant are not expected.
The NHS website provides advice for patients on the use of specific medicines in breastfeeding.
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.