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Zofran Side Effects

Morning sickness is estimated to affect up to 85 percent of women during the first 6-12 weeks of pregnancy. An estimated one percent of women experience extreme morning sickness, known as hypermesis gravidarum, the side effects of which can include dehydration, hospitalization, muscle wasting, drastic weight loss, and near-constant vomiting.

In recent years, some doctors have prescribed the anti-nausea drug Zofran (odansetron) for the treatment of these symptoms. While  Zofran may have a calming effect on the stomach and gastrointestinal tract, its effects on the developing fetus are unknown. In recent years scientific research has questioned whether or not Zofran is safe for developing fetuses when taken by pregnant mothers, with some research suggesting the possibility of a link between odansetron and an increased risk of birth defects, including cardiac malformations. While no conclusive causal link has been established between Zofran and birth defects, scientific evidence that the drug is safe for use in pregnant women is also lacking.

Troubling questions remain for women suffering from the debilitating effects of morning sickness, and their physicians – is Zofran an effective treatment, or can it cause more harm than good?

History of Zofran

The drug Zofran was developed, manufactured and marketed by the drug giant GlaxoSmithKline in the 1990’s for the treatment of nausea and vomiting associated with chemotherapy. Though some doctors have prescribed Zofran for “off label” use by pregnant women, it was never approved by the FDA for the treatment of morning sickness or hyperemesis gravidarum.

Zofran works by inhibiting the presence of serotonin in the blood stream. In so doing, the body is encouraged to empty its gastric contents, thereby eliminating the intense feelings of sickness commonly associated with early pregnancy.

Zofran was never tested on pregnant women, and its use to treat morning sickness was never considered by the FDA when it issued its approval of the drug. Zofran lawsuits filed on behalf of children with birth defects allege that the drug maker intentionally marketed the drug for this “off label” use despite knowing that fetal injuries could result.

Zofran side effects in the developing fetus

More scientific research is needed to fully determine the relationship between Zofran use during pregnancy and side effects in the unborn child.

Scientists continue to gather data to determine if any of these complications could be caused by Zofran use:

  • Heart defects, including murmurs, artrial septal defect, ventricular hypertension, and aortic arch hypoplasia
  • Facial dysmorphia
  • Toxicity
  • Intrauterine death
  • Fetal growth restriction
  • Renal malformation
  • Jaundice
  • Cleft palate

Pregnant women taking Zofran may also be at risk of serious side effects. The FDA has issued warnings about the increased risk for abnormal heart rhythms and even the potentially fatal Torsades de Pointes in Zofran users.

The Zofran label indicates it can cause severe drowsiness, headache, and difficulty concentrating. Patients are instructed to avoid the operation of machinery or a vehicle while under the influence of Zofran. Other less common side effects of Zofran include blurred vision, temporary blindness, decreased heart rate, shortness of breath, anxiety, agitation, shivering, lightheadedness, and cessation of urination. Zofran is also indicated to possibly impact thinking and decision-making due to its impact on brain chemical balance.

Did GlaxoSmithKline test Zofran on animals? 

Allegedly, the maker of this anti-nausea drug has known about the potential for fetal harm since Zofran was first introduced in the 1990’s. Whether or not this claim is true, it is certain that the company never took steps to test the drug in pregnant women. As far back as the 1980’s, according to recent product liability lawsuits, the drug maker tested odansetron in laboratory animals, which revealed the occurrence of fetal death, toxicity and malformations of the fetuses. Plaintiffs claim that these findings were never reported to the public.

In 2012, the federal government charged GlaxoSmithKline with marketing Zofran for off-label uses and paying kickbacks to doctors to prescribe it and other drugs. These allegations formed a part of a larger civil and criminal case brought against GSK by the Department of Justice, which was resolved when the drug maker agreed to a $3 billion settlement. GlaxoSmithKline has admitted no liability in regard to off-label marketing of Zofran, and continues to sell the drug.

Options for women concerned about Zofran and heart defects

Currently, Zofran is classified as a Category B drug within the context of use by pregnant women. A Category B drug has neither been deemed dangerous for use in expecting mothers, nor is it considered completely safe. In most cases, drugs falling in this category have not been researched to the point that the medical community feels confident classifying it as safe for use by pregnant women. In the words of the FDA, “animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.” Other drugs considered Category B medications include metformin, hydrochlorothiazide, cyclobenzaprine, amoxicillin and pantoprazole.

Pregnant women who are currently prescribed Zofran are encouraged to meet with their healthcare provider to determine the best course of action moving forward. As with any major medical decision, patients have a right to a full explanation of potential risks and benefits of any course of treatment. Recent research has rendered conflicting results regarding potential Zofran side effects in fetuses, though at least two studies have shown a verifiable risk.

For some women, the risks of abnormal fetal development may be outweighed by the importance of limiting the effects of extreme morning sickness. For others, the potential fetal impact may be too great to justify continuing with the drug. In all cases, thorough and well-discussed medical analysis between patient and doctor is necessary to ensure the best and safest outcome for mom and baby.

  1. RX List – Zofran Side Effects
  2. FDA – Zofran Label,020605s014,020781s014lbl.pdf
  3. American Pregnancy Association – Pregnancy Category B
  4. FDA Drug Safety Communication - Abnormal heart rhythms may be associated with use of Zofran (ondansetron)
  5. FDA Drug Safety Communication - New information regarding QT prolongation with ondansetron (Zofran)
  6. FDA - Potential Signals of Serious Risks/New Safety Information Identified by the FDA Adverse Event Reporting System (FAERS) between January– March 2013
  7. Canadian Health – Zofran Fact Sheet
  8. WKRG – Zofran Lawsuit Alleges GSK Failed To Disclose Zofran Dangers
  9. Mayo Clinic – Serotonin Syndrome
  10. NIH - “Medications Used to Treat Nausea and Vomiting of Pregnancy and the Risk of Selected Birth Defects”
  11. American Journal of Obstetrics & Gynecology - Treating morning sickness in the United States—changes in prescribing are needed
  12. Int Soc Pharmacoepidemiol – “Ondansetron use in early pregnancy and the risk of congenital malformations”
  13. Toronto Star – Birth Defects Blamed On Unapproved Morning Sickness Treatment
  14. Department of Justice - GlaxoSmithKline to Plead Guilty and Pay $3 Billion to Resolve Fraud Allegations and Failure to Report Safety Data