Ondansetron (Zofran) Safety During Breastfeeding
Ondansetron is safe to use while breastfeeding, with no waiting period required before nursing, based on authoritative guideline recommendations and pharmacokinetic modeling showing minimal infant exposure. 1, 2
Guideline-Based Recommendation
The Association of Anaesthetists 2020 guideline explicitly endorses ondansetron as compatible with breastfeeding, categorizing it alongside other safe anti-emetics without requiring special precautions or pump-and-dump protocols. 1, 2
The guideline acknowledges that while no human studies exist on ondansetron transfer into breast milk, animal data and pharmacokinetic principles support its safety profile during lactation. 1
Both intravenous and oral formulations are considered acceptable for breastfeeding women at standard clinical doses used for nausea and vomiting management. 2
Supporting Evidence on Infant Exposure
A 2022 physiologically-based pharmacokinetic model using data from 78 breastfeeding women demonstrated that ondansetron passage into breast milk results in a relative infant dose of only 3.0%, well below the 10% safety threshold typically used to assess medication compatibility with breastfeeding. 3
The predicted daily infant dose was calculated at 0.005 mg/kg/day, an extremely low exposure level that supports safe breastfeeding while mothers receive ondansetron. 3
The FDA drug label states that ondansetron presence in human milk is unknown, but notes that when drugs appear in animal milk, they are likely present in human milk—however, this does not contraindicate breastfeeding use. 4
Practical Clinical Application
No waiting period or "pump and dump" is necessary after ondansetron administration; mothers can breastfeed immediately following treatment. 1, 2
Standard dosing for nausea is 4-8 mg orally every 8 hours as needed, which is appropriate for breastfeeding women. 2
Ondansetron can be used for acute nausea episodes, hyperemesis gravidarum in early pregnancy while still nursing an older infant, or peri-operative nausea management. 1, 5
Important Safety Considerations
Special caution is warranted in mothers with underlying heart disease due to potential QT interval prolongation—this is a maternal safety concern, not related to infant exposure through breast milk. 1, 2
The cardiac risk applies to the mother receiving the medication, not the breastfed infant, and should be considered when prescribing to women with known cardiac conditions. 2
Many breastfeeding women seeking information about ondansetron are nursing older infants (>6 months in 96% of cases, >1 year in 71% of cases) while experiencing nausea in a subsequent pregnancy, a clinical scenario not typically addressed in treatment guidelines. 5
Common Clinical Pitfall
Restrictive product labeling from manufacturers often causes unnecessary concern and potential premature weaning, despite guideline support for ondansetron use during lactation. 5
Healthcare providers should prioritize evidence-based guideline recommendations over manufacturer warnings that state "unknown if present in human milk," as this standard disclaimer does not reflect actual clinical risk assessment. 4, 5