Increasing ondansetron use reported against NVP in the United States

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Ondansetron is the most common prescription antiemetic used to manage nausea and vomiting in pregnancy (NVP) among US patients, with an increase of use observed since 2006, according to a recent study published in JAMA Network Open.¹

Among patients with NVP, the recommended first-line therapy by the American College of Obstetricians and Gynecologists (ACOG) in 2004 was either pyridoxine or a combination of doxylamine and pyridoxine. ACOG also recommended ondansetron be used only as a last-line therapy.¹

These guidelines were published in 2004, with an update in 2018 recommending ondansetron for use as a third-line therapy. Data about antiemetic use among NVP is currently lacking following these updates.¹

In 2017, a US Government study evaluated the increasing use of ondansetron among pregnant women in the United States.² Antiemetic use among pregnant women from 2001 to 2015 was observed. A validated algorithm was used to identify live birth pregnancies, and antiemetic use was reported by trimester, year, and formulation.

Ondansetron had a prevalence of 15.2% across over 2.3 million pregnancies. In comparison, promethazine had a prevalence of 10.3%, metoclopramide a prevalence of 4%, and doxylamine or pyridoxine a prevalence of 0.4%. Ondansetron use was reported in 22.2% of pregnancies in 2014 vs under 1% of pregnancies in 2001.²

Investigators conducted a study to evaluate prescription antiemetic treatment patterns among NVP, including monotherapy, switching, and combination therapy during the first trimester.¹ Pregnant individuals aged 12 to 55 years were identified using Merative MarketScan Commercial Claims data from 2005 to 2019.

Continuous health plan enrollment for at least 90 days before conception and 30 days after end of pregnancy was required for inclusion. Pharmacy dispensing claims during the first trimester were assessed to categorize prescription antiemetic treatment use.¹

Investigators defined combination use as “a prescription fill for a second antiemetic during the active days’ supply of a different (first) antiemetic and a refill of the first antiemetic during the active days’ supply of the second.” Switching therapy was defined as using multiple antiemetics while not meeting these criteria.¹

There were 3,303,463 pregnancies included in the analysis, 14.3% of which were among patients using prescription antiemetics. Of these patients, 30.7% were aged 25 to 29 years, 34% 30 to 34 years, and 18.8% over 34 years.¹

Prescription monotherapy was reported in 1096 per 10,000 pregnancies, switching in 314 per 10,000 pregnancies, and combination therapy in 38 per 10,000 pregnancies. Ondansetron was the most common monotherapy, promethazine into ondansetron the most common switching, and promethazine-ondansetron the most common combination.¹

A link between ondansetron monotherapy and increased NPV severity was reported from 2005 to 2006. In 2007, patients using ondansetron monotherapy were more likely to have clinicians besides obstetrician-gynecologists, but this regimen was not linked to maternal NVP severity or other clinical characteristics.¹

No factors were reported for switching. However, an association was reported between prior antiemetic treatment and ondansetron combination.¹

These results indicated ondansetron as the most common prescription antiemetic among patients with NVP in the United States. Though ondansetron use was linked to clinician types rather than maternal characteristics, it remains recommended as third-line therapy if other options fail.¹

References

1. Thai TN, Brown J, Schmidt S, Maro J, Rasmussen SA, Winterstein AG. Use of prescription antiemetics among US commercially insured pregnant patients, 2005-2019. JAMA Netw Open. 2024;7(10):e2440414. doi:10.1001/jamanetworkopen.2024.40414
2. Taylor LG, Bird ST, Sahin L, et al. Antiemetic use among pregnant women in the United States: the escalating use of ondansetron. Pharmacoepidemiol Drug Saf. 2017;26(5):592-596. doi:10.1002/pds.4185