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Zofran Side Effects


When used during pregnancy, the anti-nausea medication Zofran has been associated with birth defects, including heart defects and cleft palate. The FDA has also issued safety warnings about deadly heart problems, including a deadly abnormal heart rhythm disorder called Torsade de Pointes.

What is Zofran?

Zofran (ondansetron) is an anti-nausea drug created by GlaxoSmithKline (GSK). It was approved in 1991 by the U.S. Food and Drug Administration (FDA), and is now available as a generic medication called Onsandestron. Zofran works by inhibiting 5-HT3 serotonin receptors.

Zofran is primarily prescribed to treat nausea and vomiting in patients undergoing chemotherapy. It is also prescribed in lower doses to patients after surgery.

Zofran and Pregnancy

Zofran is commonly used “off-label” to prevent nausea and vomiting associated with morning sickness during the first trimester of pregnancy. Unfortunately, this is a critical time in fetal development when many birth defects can occur.

Zofran is not approved by the FDA for morning sickness and it is “Pregnancy Class B,” which means placebo-controlled studies have only been conducted in animals. Although animal studies found no evidence of pregnancy side effects, a growing number of population-based studies have found evidence linking Zofran and birth defects.

In August 2013, Zofran was linked to a 30% increased risk of birth defects and a doubled risk of heart defects in the study, “Ondansetron use in early pregnancy and the risk of congenital malformations.”.

Conclusions were based on data from nearly 900,000 pregnancies in Denmark between 1997 and 2010. Birth defects occurred in nearly 5% of the 1,250 women who used Zofran in the first trimester, compared to 3.5% of women who did not. Metroclopramide, another anti-nausea drug sometimes used for morning sickness, was not associated with birth defects.

Interestingly, six months before this study was published, the New England Journal of Medicine published another study based on 600,000 births in Denmark that found no evidence of fetal harm. However, 50% of the women took Zofran after the first trimester, when their baby was no longer at risk of many birth defects.

More recently, an investigative report by the Toronto Star found nearly two dozen case reports linking Zofran with heart defects, kidney problems, musculoskeletal abnormalities, and other birth defects.

In December 2014, Swedish researchers looked at data on 1,400 Zofran-exposed pregnancies from 1998-2012 and found that Zofran doubled the risk of septal heart defects. Results were published in Reproductive Toxicology.

Another recent study, published by BioMed Research International in December 2013 by Australian researchers, linked the use of Zofran in the first trimester with a non-significant 20% increased risk of birth defects and higher rates of kidney defects. However, the study was too small to estimate the risk of individual birth defects with any precision.

Zofran Pregnancy Side Effects

Our attorneys are investigating cases involving:

Other pregnancy side effects of Zofran may include:

  • Fetal growth restriction (poor growth in the womb)
  • Jaundice
  • Kidney defects
  • Life-threatening complications for mother (serotonin syndrome, irregular heart rhythm, Torsade de Pointes, etc.)
  • Fetal or maternal death

Zofran Side Effects

Zofran is associated with life-threatening cardiac side effects. The drug can interfere with electrical activity in the heart, which may cause a fatal irregular heart rhythm disorder. Cardiovascular side effects of Zofran may include:

  • Chest pain, tightness, or discomfort
  • Irregular heart rhythm
  • Abnormally fast, slow, or weak pulse
  • QT interval prolongation
  • Torsades de Pointes
  • Ventricular arrhythmia

Zofran is also associated with the following serious side effects:

  • Muscle weakness
  • Fatigue
  • Dizziness
  • Headaches
  • Allergic reaction
  • Swelling of the face, lips, tongue
  • Fever
  • Diarrhea
  • Constipation
  • And more

Cardiovascular Zofran Side Effects

Zofran can interfere with electrical activity in the heart. This can cause a disorder called QT interval prolongation, in which the electrical charge in the heart takes longer than 440 milliseconds to recover between each beat. The 32-mg dose of Zofran increases the QT interval by an average of 20 milliseconds, and the 8-mg dose is associated with a 6 millisecond change.

In severe cases, QT interval prolongation longer than 600 milliseconds can lead to Torsades de Pointes. The heart may flutter ineffectively and suddenly stop beating. This can cause a loss of consciousness, low blood pressure, and sudden death.

FDA Warnings for Zofran Side Effects

The FDA first warned about Zofran side effects in September 2011. The agency updated the label on Zofran to warn that it could increase the risk of “developing prolongation of the QT interval of the electrocardiogram, which can lead to an abnormal and potentially fatal heart rhythm, including Torsades de Pointes.”

After this warning, the FDA required the manufacturer to study what dose of Zofran was associated with cardiac risks. The study was completed in June 2012, and found that a single 32-mg dose of Zofran was associated with QT interval prolongation.

Serotonin Syndrome

March 2013 — The FDA has identified a “potential safety issue” about the risk of serotonin syndrome from Zofran and other drugs in the 5-HT3 class, which work by influencing serotonin levels. The risk of serotonin syndrome may be compounded in individuals who also use SSRI antidepressants, which also influence serotonin

Serotonin syndrome side effects:

  • Agitation or restlessness
  • Confusion
  • Rapid heartbeat and high blood pressure
  • Loss of muscle coordination, twitching or rigid muscles
  • Heavy sweating
  • Diarrhea
  • High fever
  • Seizures
  • Irregular heartbeat
  • Loss of consciousness

Zofran Recall

More than a year after the FDA first warned about Zofran side effects, the agency recalled 32-mg intravenous Zofran in December 2012. The recall is unlikely to affect many patients because the dose makes up only a small percentage of the drug’s market.


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