If your nausea and vomiting is so severe that the first and second line treatments have not suppressed symptoms to an adequate level then your doctor may prescribe Ondansetron (known also as Zofran). It is a relatively new medication which was originally used to treat nausea and vomiting caused by chemotherapy for cancer patients but is increasingly used for Hyperemesis Gravidarum and you are likely to read about it on internet forums and websites.
Research regarding the saftey of this drug is increasing. A study in Canada by the Motherisk program looked at foetal outcomes for mothers who had taken Ondansetron as well as mothers who had taken other anti emetics and compared them to the baseline rate of birth defects. It was found that there was no increase in the rate of birth defects for mothers who had taken Ondansetron. An abstract of the study and others can be seen on our Downloads page. The HelpHer site also has further information.
A more recent study in Denmark by Pasternak et al (2013) looked at 1,233 women exposed to ondansetron between weeks 7-12 of pregnancy (from LMP) and compared the birth defect rate with that of 4,932 women not exposed to ondansetron. They found that the birth defect rate was 2.9%, at birth, for both groups. The literature review found the baseline risk of 1-3% for a major congenital birth defect at birth for all pregnancies which is in line with this research. The reference and abstract for the article is on our references page. This is very encouraging research.
It is a prescription only medication and side effects include constipation and headaches. it can be taken orally, as an injection, as a suppository (inside your rectum) or as an 'oro-dispersal' tablet (melted on the tongue).
Einarson A. 2004. The safety of ondansetron for nausea and vomiting of pregnancy: a prospective comparative study. International Journal of Obstetrics and Gynaecology, 111, 940-943.