Ondansetron: Birth defects

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Ondansetron is a 5-HT3 receptor antagonist indicated for the treatment of nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy. It is also indicated for prevention and treatment of postoperative nausea and vomiting.



The National Pharmaceutical Regulatory Agency (NPRA) received information from the European Medicines Agency (EMA) on the association of ondansetron with the risk of birth defects. EMA requested all product registration holders of ondansetron-containing products to update product information with this new safety information.1

This action was taken following two recent epidemiological studies based in the United States related to the use of ondansetron in pregnancy, published by Zambelli-Weiner et al. (2019) and Huybrechts et al. (2018).2 These studies suggested an association between ondansetron exposure during the first trimester of pregnancy and an increased risk of orofacial cleft malformations. However, there were conflicting results for cardiac malformations.3,4 The same signal has been identified by the United Kingdom, showing consistency with the results from previous studies.1


Adverse Drug Reaction Reports

NPRA has received 29 reports with 42 adverse events suspected to be related to ondansetron. However, no event related to birth defects has been reported.5


Advice for Healthcare Professionals

  • Ondansetron is not indicated for treatment of nausea and vomiting in pregnancy and should not be used in the first trimester of pregnancy.
  • The risk of birth defects associated with ondansetron-use should be considered before prescribing ondansetron to patients.
  • If women of childbearing potential require treatment with ondansetron, they should be informed and understand the potential risk of birth defects associated with ondansetron use in pregnancy and should consider the use of contraception.
  • Please report all suspected adverse events associated with ondansetron-containing products to the NPRA.



  1. European Medicine Agency (2019). PRAC recommendations on signals. https://www.ema.europa.eu/en/documents/prac-recommendation/prac-recommendations-signals-adopted-8-11-july-2019-prac-meeting_en.pdf
  2. European Medicine Agency (2019). PRAC minutes of the meeting. https://www.ema.europa.eu/en/documents/minutes/minutes-prac-meeting-12-15-march-2019_en.pdf
  3. Huybrechts KF et al. (2018): Association of maternal first-trimester ondansetron use with cardiac malformations and oral clefts in offspring. JAMA 320(23):2429-2437.
  4. A Zambelli-Weiner et al. (2019): First trimester ondansetron exposure and risk of structural birth defects. Reprod Toxicol 83:14-20.
  5. The Malaysian Adverse Drug Reaction database, NPRA [Accessed: 7th November 2019]



This publication is aimed at health professionals. The information is meant to provide updates on medication safety issues, and not as a substitute for clinical judgement. While reasonable care has been taken to verify the accuracy of the information at the time of publication, the NPRA shall not be held liable for any loss whatsoever arising from the use of or reliance on this publication.



National Pharmaceutical Regulatory Agency (NPRA)

Lot 36, Jalan Universiti (Jalan Prof Diraja Ungku Aziz), 46200 Petaling Jaya, Selangor, Malaysia.

  • Phone: +603-7883 5400




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