Ondansetron in Pregnancy and Breastfeeding
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Ondansetron (ZofranŽ tablets and injection)
Antiemetic. Selective 5-HT 3 receptor antagonist .
Molecular weight: 365.9. Plasma protein binding of ondansetron as measured in vitro was 70% to 76%, with binding constant over the pharmacologic concentration range (10 to 500 ng/mL).

Reproduction studies have been performed in pregnant rats and rabbits at daily oral doses up to 15  and 30 mg/kg per day respectively, and have revealed no evidence of impaired fertility or harm to the fetus due to ondansetron [1].

In one case report ondansetron 8 mg IV TID was used to successfully treat hyperemesis gravidarum in a woman from approximately 11 to 13 weeks gestation. She gave birth to a term healthy infant [2].  Tincello and Johnstone also used ondansetron intermittently every trimester to  treat hyperemesis gravidarum in one patient with no apparent adverse effects on the mother or infant [3].

In a randomized controlled trial comparing ondansetron with promethazine for the treatment of hyperemesis gravidarum 15 patients were treated with ondansetron at a mean gestational age of 11 weeks'. Patients were given an initial dose of ondansetron 10 mg IV with additional doses as need TID. Ondansetron demonstrated no benefit over promethazine in patients hospitalized for hyperemesis gravidarum. The authors of the study suggested that increasing ondansetron dosages or using a continuous infusion might have improved the treatment response. Pregnancy outcomes were not reported for either group [4].

In two additional case reports of pregnant women treated with ondansetron during the third trimester both mothers delivered normal infants [5, 6].

A prospective observational study by The Motherisk and The Mothersafe Programs compared the pregnancy outcomes of 176 women who had used ondansetron during the first trimester of pregnancy with women who had used other antiemetics (including Diclectin, metoclopramide, phenothiazines, and ginger) during the first trimester, and women who had nonteratogenic exposures during the first trimester. There was no statistically significant difference between the three groups in terms of major malformations, live births, miscarriages, stillbirths, therapeutic abortions, birthweight , or gestational age at the time of delivery. However, in the ondansetron group, there were three cases of hypospadias which was not statistically significant. The authors of the study point out that the lack of statistical  significance may have been due to the small sample size [7].

While the above reports are reassuring the number of reported cases is too small to draw firm conclusions regarding the teratogenic risk of ondansetron in human pregnancy.

BREAST FEEDING: It is not known whether ondansetron is excreted into human milk.


1. Physicians Desk Reference 57th ed. Montvale, NJ: Thomson PDR; 2004: 1680-2
2. Guikontes E, et al. Ondansetron and hyperemesis gravidarum.Lancet. 1992; 340: 1223.  MEDLINE
3. Tincello DG and  Johnstone MJ.Treatment of hyperemesis gravidarum with the 5-HT3 antagonist ondansetron (Zofran).Postgrad Med J. 1996;72:688-9. MEDLINE
4. Sullivan CA, et al. A pilot study of intravenous ondansetron for hyperemesis gravidarum. Am J Obstet Gynecol. 1996 ; 174: 1565-8.MEDLINE
5. World MJ: Ondansetron and hyperemesis gravidarum.Lancet. 1993; 341: 185. MEDLINE
6. Arango HA, et al. Management of chemotherapy in a pregnancy complicated by a large neuroblastoma.Obstet Gynecol. 1994 ;84:665-8. MEDLINE
7.Einarson A. et al., The safety of ondansetron for nausea and vomiting of pregnancy: a prospective comparative study.BJOG. 2004;111:940-3. MEDLINE

Created: 11/17/2000
Updated: 11/30/2002
Updated: 2/17/2004
Updated: 10/28/2004

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