Zofran during Pregnancy: Everything You Should Know


50% of pregnant women suffer from morning sickness. 15% require anti-emetic medications. One of the most common anti-emetics is Zofran, better known by its generic name, Ondensetron. Almost 1 million pregnant women take Zofran each year to treat morning sickness. The problem with morning sickness is that it affects women mostly in the first trimester of pregnancy. That is also the time when the fetus develops the most. This makes it all the more important to know about the safety of the medications you take because a wrong medication can lead to birth defects in the child.

So, is Zofran safe? Let’s find out.

About Zofran

  • Introduction

Ondensetron was originally created in 1984 to treat moderate and extreme nausea and vomiting in cancer patients undergoing chemotherapy.

It was later marketed by the pharmaceutical company Glaxosmithkline as Zofran.

  • Current Use

  • Approved uses
  • Prevention and treatment of chemotherapy induced nausea vomiting
  • Prevention of post-operative nausea and vomiting
  • Off-label Use
  • Morning sickness in pregnancy
  • Hyperemesis Gravidarum (extreme vomiting in pregnancy)
  • Uremic and cholestatic itching.

Zofran during Pregnancy

  • Dosage Form and Dose

Zofran is available in the form of tablets (4mg or 8mg), liquid preparations and injections.

  • How Does Zofran Work

Zofran blocks the ‘serotonin’ receptors (5HT3 antagonist). These receptors are responsible for inducing the feeling of nausea and subsequent vomiting. It is metabolized in liver and remains in the body for 5 to 7 hours.

  • Common Side Effects

The common side effects of Zofran are headache and constipation.

Zofran In Pregnancy

Zofran is not approved by US Food and drug administration (FDA) for use in pregnancy. The FDA lists Zofran as a ‘category B drug’ as far as safety in pregnancy is considered. This means “No well controlled studies have been conducted on the effect of the drug in pregnant women and evidence of safety is lacking.”

On the other hand, FDA hasn’t banned or stopped Zofran from being prescribed in pregnancy. However, a periodic warning against its use has been issued.

It has been demoted as American College of Obstetrics and Gynecology. (ACOG)

Doctors are legally required to inform about the risks of taking the drug to all pregnant women before prescribing it.


Researches Conducted And Results

The researches on the use of Zofran in pregnancy have been ill-conducted and have given contradictory results. Two inadequate methods have been applied to collect data.

  • Looking at registries of children born with birth defects and asking mothers what medications they had taken during pregnancy based on memory.
  • Comparing outcomes in children whose mothers received ondensetron as prescription to those that did not.

These methods have not been well controlled and lack authenticity. However, the different researches published have been included here with results. The results have not been consistent with each other further adding to the notion of inadequate proof.

  • In 2004, scientists from Canada and Australia reported that no significant risk of birth defects was found in mothers taking Zofran
  • A Danish study (2004-2011) concluded that Zofran was not a high risk medication if taken in the second half of first trimester.
  • A CDC cohort (2011) concluded that Zofran increased the risk of fetal heart defects by two folds.
  • A study published in 2014 in New England Journal Of Medicine claimed that Zofran poses no risk to developing fetus. It reported no increased risk of preterm labour or low birth weight.

Recently, Glaxosmithkline has been subjected to over 200 lawsuits for “unlawfully promoting” the unapproved and off label use of Zofran (to pregnant mothers) and some other drugs and “failing to report” safety data to FDA which may have resulted in birth defects. One of these lawsuits was filed by the Department of Justice which the pharmaceutical giant settled for 3 billion dollars. They however have since refused the allegations to be true.

Risks Supposedly Associated With Use Of Zofran In Pregnancy

  • To mothers:
  • Use of Zofran is ‘possibly’ linked to Serotonin Syndrome in pregnant mothers. This syndrome is characterized by increased nerve cell activity in brain. The symptoms are anxiety, neuromuscular changes, confusion, agitation and neuromuscular changes.
  • Zofran is known to cause arrhythmias if taken intravenously in doses greater than 16 mg. (US FDA recommendations of drug safety)
  • Immediately visit a doctor if these symptoms are present after taking Zofran
  • Dizziness
  • Shortness of breath
  • Extreme fatigue
  • Irregular heartbeat
  • To fetus:
  • Cleft palates
  • Heart defects including valvular and septal defects
  • Jaundice
  • Musculoskeletal abnormalities


The risks with Zofran present but not very prevalent. It should only be tried after other therapies have failed but if morning sickness is extreme or hyperemesis poses a risk of dehydration and shock, it is better to take the drug than suffer as these conditions pose a bigger threat to fetus and you.

Alternate therapies for morning sickness

  • Dietary Changes: A simple change in the diet can be the solution to the problem of nausea and vomiting in pregnancy. Gynecologists suggest frequent meals with simple carbohydrates like crackers instead of complex food.
  • Eliminate Triggers: Most of the time, a trigger factor is responsible for vomiting in pregnancy. The trigger can be anything ranging from certain smells, food to even certain thoughts! Identifying and avoiding the trigger can go a long way in preventing morning sickness.
  • Keep Your Body Hydrated: Pregnancy leads to an increase in the water requirements of the body. And with all that peeing and vomiting, make sure to keep yourself hydrated.
  • Ginger drinks/formulations: Keeping ginger flavored lozenges in your mouth can help relieve the nausea. Ginger tea is also a drink you may try.
  • Diclegis (vitamin B6 with doxylamine) : This is the only FDA approved drug for nausea, vomiting in pregnancy. It is a category A safe drug. Vitamin B6 alone may also help in dealing with vomiting.

Since every pregnancy is different, it is upto you and your doctor to discuss and decide the drug suitable for you. Knowing about the drug will only make the deciding process easier for you.

Stay informed. Stay safe!


Happy parenting!