USE OF ONDANSETRON IN PREGNANCY

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(Date of issue: September 2019, Version: 3)

This is a UKTIS monograph for use by health care professionals. For case-specific advice please contact UKTIS on 0344 892 0909. To report an exposure please download and complete a pregnancy reporting form. Please encourage all women to complete an online reporting form.

Summary

Ondansetron is a selective 5-HT3 serotonin antagonist used in the treatment of chemotherapy-induced and post-operative nausea and vomiting, and off-licence for nausea and vomiting in pregnancy (NVP) and hyperemesis gravidarum (HG). 

The currently available data do not provide evidence that ondansetron use in the first trimester of pregnancy is associated with an increase in the overall malformation rate.

Although small numbers of studies have described statistically significant increased risks of both overall and specific cardiac malformations, namely septal defects, these data are conflicting. Furthermore, most of these studies did not utilise disease-matched ondansetron-unexposed control groups, therefore the possibility of confounding cannot be excluded.

Several studies have suggested that associations may exist between maternal ondansetron use and fetal orofacial clefts, specifically cleft palate alone. Whilst the available data are conflicting, should a true association exist, the absolute risk is likely to remain small (background rate ~0.11% vs. ondansetron-exposed rate ~0.14%).

Four studies which utilised data from three unique datasets have also suggested possible associations with overall or specific renal malformations. These observations require further investigation before adequate conclusions can be drawn.

Studies investigating the risk of miscarriage, intrauterine death/stillbirth, low birth weight, preterm delivery and neurodevelopmental impairment are more limited than those investigating malformation risks, but do not currently provide evidence suggestive of an increased risk of these outcomes following maternal ondansetron use in pregnancy.

Ondansetron should only be used during pregnancy where the benefits of treatment are considered to outweigh any potential fetal risks. Exposure to ondansetron at any stage in pregnancy would not usually be regarded as medical grounds for termination of pregnancy or any additional fetal monitoring. However, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.

This document is regularly reviewed and updated. Only use full UKTIS monographs downloaded directly from TOXBASE.org to be sure you are using the most up-to-date version. The summaries of these monographs are openly available on UKTIS.org.

This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to health care professionals at www.toxbase.org.

If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from TOXBASE.org or UKTIS.org to ensure you are using the most up-to-date version.