Which is the best antiemetic for nausea and vomiting in pregnancy?

It is best to avoid drugs, if possible, during pregnancy.

Typically, dietary changes and avoidance of triggers are tried first:

  • Take meals and snack when hungry to avoid empty stomach, which can aggravate nausea.
  • Avoid coffee, odorous, high-fat, acidic and/or very sweet foods.
  • Eat meals and snacks slowly and in small amounts every one to two hours to avoid overly full stomach, which can also aggravate nausea.
  • Choose high-protein, salty, low-fat, bland and/or dry foods.
  • Take fluid at least 30 min before solid food. Sip fluid in small amounts. Avoid triggers (e.g., odours, stuffy rooms, etc.).
  • Ginger-containing foods can suppress nausea and vomiting.

If dietary changes and avoidance of triggers do not work, pyridoxine (vitamin B6) supplementation is usually tried next. This can improve nausea, but is usually less effective at preventing vomiting.

If vitamin B6 supplementation does not work, a first-generation antihistamine (muscarinic antagonist and H1 receptor antihistamine) is used. The choice is usually doxylamine, an old antihistamine. Doxylamine is usually still combined with vitamin B6. Older drugs are preferred, as we have greater historical knowledge of use in pregnancy. Newer drugs are generally avoided as clinical trials rarely include pregnant women and so there is little information available on their safety during pregnancy.

If vitamin B6 supplementation and doxylamine do not work, then any of the other older H1/M1 blockers (e.g. diphenhydramine) or D2 blockers (e.g. metoclopramide) is used alone or in combination. Again the older agents are used as there is more accumulated knowledge giving some confidence of safety in pregnancy. Only if none of these approaches work is the newer class of 5-HT3 antagonists tried and the agent chosen is typically either ondansetron or granisetron (older agents within the class for which there is some history of use in pregnancy).