(232) Trends in Antiemetic Medication Use in Pregnancy in An Integrated Health System in the US, 2010–2021

Publication Number: 563

Background: Three-quarters of pregnant people have nausea or vomiting; many use antiemetic medications to manage these symptoms. Evidence from small trials suggests that the antiemetic ondansetron may provide effective symptom relief while being better tolerated than other antiemetics. However, evidence from some observational studies suggests ondansetron may be associated with malformations, leading to a 2019 warning against first trimester use by the European Medicines Agency. A US study reported prenatal ondansetron use increasing dramatically from 2006–2014, but no studies have examined whether this increase has continued.

Objectives: To describe recent trends in prenatal ondansetron use, as well as any prenatal antiemetic use, in a US integrated health system, particularly after 2014.

Methods: We used electronic health record data from Kaiser Permanente Washington to study pregnancies in women age 15–49 from 2010–2021. We assessed prescription antiemetic exposure using outpatient pharmacy dispensings. For each year, we calculated the proportion of pregnancies exposed to ≥1 dispensing of ondansetron, promethazine, metoclopramide, doxylamine with pyridoxine (combination medication), pyridoxine, or prochlorperazine, and constructed 95% confidence intervals (CIs).

Results: There were 79,309 eligible pregnancies (median maternal age: 31 years). Overall, 20% of pregnancies (n=15,727) were exposed to antiemetics. Use rose from 16% (95% CI: 15–17%) in 2010 to peak at 24% (95% CI: 23–25%) in 2014, then decreased to 17% (95% CI: 16–18%) in 2017, before rebounding somewhat to 21% (95% CI: 20–22%) by 2021. Ondansetron was the most commonly used, increasing from 7% (95% CI: 7–8%) of pregnancies in 2010 to 17% in 2014 (95% CI: 17–18%), followed by a downturn to 11% by 2017 (95% CI: 11–12%), before increasing back nearly to peak levels by 2021, at 17% (95% CI: 16–18%). The proportion of antiemetic-exposed pregnancies using ondansetron increased from 46% in 2010 to 79% by 2021.

Conclusions: In this US population, over one-fifth of pregnancies were exposed to prescription antiemetics in 2021. Ondansetron use did not continue to increase after 2014; Ondansetron use did not continue to increase after 2014; instead, use decreased through 2017, then returned close to peak levels by 2021. Ondansetron increasingly comprised the vast majority of antiemetic use, with 79% of antiemetic-exposed pregnancies using ondansetron by 2021.