While it is best not to take any medicines or drugs (other than Folate, Iodine and Multivitamins – and other vital medicines for specific medical conditions as required) during the first trimester (until about the end of week 12), some women do need to take medicines for a variety of reasons.
One common reason is to treat troublesome or severe nausea and vomiting (Hyperemesis). Untreated, severe Hyperemesis can be life-threatening, if severe dehydration occurs.
A number of different drugs are commonly used to treat nausea and vomiting in pregnancy – such as Metoclopramide (“Maxolon”), Doxylamine (“Restavit”), Pyridoxine (Vitamin B6) and Ondansetron (“Zofran”). Below is some information about the treatment of nausea and vomiting in pregnancy and some specific notes about Ondansetron:
Information from the Mothersafe site in NSW:
Hyperemesis – Mothersafe (NSW)
Information about the drug Ondansetron (“Zofran”):