IV Ondansetron in the First Trimester of Pregnancy

Today’s pearl is an update on the use of ondansetron in pregnant patients.

What to do when first line agents aren’t effective?

In the ED, we commonly treat pregnant patients with nausea and vomiting (N/V) that is unresponsive to non-pharmacologic therapies. A common question is whether it is safe to use IV ondansetron in the first trimester. A 2018 ACOG Bulletin outlined an algorithm for managing N/V and lists IV ondansetron as an option for dehydrated patients with persistent symptoms receiving IV fluid replacement.

A recently published study in JAMA (Huybrechts 2020) evaluated almost 24,000 patients (with propensity score matching) who received at least one dose of IV ondansetron in the first trimester. They reported the adjusted RR for cardiac malformations was 0.97 (95% CI, 0.86-1.10). For oral clefts, the adjusted RR was 0.95 (95% CI, 0.63-1.43). The authors concluded that ondansetron is not a major teratogen.

This research letter adds more evidence that IV ondansetron is a safe option, when needed, for care of our first trimester pregnant patients in the ED.


Author: Bryan D. Hayes, PharmD

Attending Pharmacist, Emergency Medicine and Toxicology, Massachusetts General Hospital; Assistant Professor of EM, Harvard Medical School

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