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Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-.

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Drugs and Lactation Database (LactMed) [Internet].

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Last Revision: February 15, 2021.

Estimated reading time: 1 minute

CASRN: 99614-02-5

image 135015969 in the ncbi pubchem database

Drug Levels and Effects

Summary of Use during Lactation

Ondansetron is frequently used for nausea during and after cesarean section, usually in doses of 4 to 8 mg intravenously.[1-4] Use during and after cesarean section appears to not affect the onset of breastfeeding.[4,5] No adverse infant effects have been reported in this setting. Use of ondansetron in nursing mothers beyond the immediate postpartum setting has not been studied well, but the drug is labeled for use in infants as young as 1 month of age. Amounts in milk are likely much less than this dose.

Drug Levels

Maternal Levels. Relevant published information was not found as of the revision date.

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

Relevant published information was not found as of the revision date.

Effects on Lactation and Breastmilk

A randomized, double-blind study compared placebo to intravenous ondansetron 4 mg given after cesarean section as prophylaxis for postoperative nausea and vomiting. There was no difference in the time of the first breastfeeding between the two groups.[3]

In a retrospective study of women undergoing cesarean section deliveries, 3 regimens were compared: dexmedetomidine before anesthesia and during delivery (n = 115), normal saline before anesthesia and during delivery and dexmedetomidine after delivery (n = 109), and normal saline before anesthesia and during delivery (n = 168). All women received ondansetron 4 mg as needed and before removal of sutures. The average total amount of ondansetron consumed in the women ranged from 6 mg to 9 mg in the various groups. The time to first production of milk was similar in all groups (25 to 28 minutes).[5]


Griffiths JD, Gyte GM, Paranjothy S, et al. Interventions for preventing nausea and vomiting in women undergoing regional anaesthesia for caesarean section. Cochrane Database Syst Rev. 2012;2012:Cd007579. [PMC free article: PMC4204618] [PubMed: 22972112]
Suppa E, Valente A, Catarci S, et al. A study of low-dose S-ketamine infusion as "preventive" pain treatment for cesarean section with spinal anesthesia: Benefits and side effects. Minerva Anestesiol. 2012;78:774–81. [PubMed: 22374377]
Jelting Y., Klein C., Harlander T., et al. Preventing nausea and vomiting in women undergoing regional anesthesia for cesarean section: challenges and solutions. Local Reg Anesth. 2017;10:83–90. [PMC free article: PMC5558589] [PubMed: 28860857]
Uerpairojkit K, Chesoh A, Budcharoentong D. Ondansetron for prophylaxis of spinal morphine induced nausea during early rooming in breastfeeding: A randomized placebo controlled trial. J Med Assoc Thai. 2017;100:1283–9. http://www​
Zhao W, Ma L, Wang J, et al. Retrospective comparison of the safety and effectiveness of dexmedetomidine versus standard of care before and during cesarean delivery in a maternity unit in Zhengzhou, China. Med Sci Monit. 2020;26:e925709. [PMC free article: PMC7592428] [PubMed: 33097682]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

Breast Feeding



Gastrointestinal Agents

Serotonin Antagonists

Serotonin 5-HT3 Receptor Antagonists

Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.


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