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Can We Use Ondansetron In Pregnancy?

February 26, 2019

Written by Vivian Lei

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In this large cohort study of over 1.8 million pregnancies, first trimester ondansetron use was not associated with cardiac malformations or total congenital malformations. However, there was a small increased risk of oral clefts (3 additional cases per 10,000 women treated).

Why does this matter?
Nausea and vomiting is common in pregnancy, especially during the first trimester which is a period of fetal organogenesis. Ondansetron has been an effective antiemetic, but prior data on the safety of ondansetron is mixed, with some studies suggesting an increased risk of cleft palate and cardiac malformations.

Still a fan of Zofran – with a caveat
Investigators performed this retrospective analyses on a large cohort of over 1.8 million pregnant patients from the nationwide Medicaid Analytic eXtract (MAX) database, which contains data regarding pregnancies resulting in live births between 2000 and 2013 among publicly insured pregnant women. Out of this cohort, 88,467 (4.9%) filled a prescription for ondansetron in the first trimester. After accounting for possible confounders, the study found the adjusted relative risk for cardiac malformations was 0.99 with a 95% CI of 0.93‒1.06. This tight confidence interval is robust evidence of no difference in risk for cardiac malformations between ondansetron-exposed live births and the control group. There was a small increase in risk of oral clefts with an adjusted risk ratio of 1.24 and a CI 1.03‒1.48. This corresponds to an absolute increase of 3 additional cases per 10,000 births among ondansetron-exposed live births. With regard to congenital malformations overall, there was no increased risk among fetuses exposed to the drug during the first trimester (adjusted risk of 1.01 with CI of 0.98 – 1.05).

This study utilized a very large data set and provides additional helpful information to clinicians when discussing risks and benefits of an effective antiemetic with pregnant patients who may have failed first-line treatments. Study limitations include the retrospective study design and cohort restriction to live births with potential for missing severe congenital malformations resulting in pregnancy losses.

Association of Maternal First-Trimester Ondansetron Use With Cardiac Malformations and Oral Clefts in Offspring. JAMA. 2018 Dec 18;320(23):2429-2437. doi: 10.1001/jama.2018.18307.

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Reviewed by Clay Smith

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