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Researchers Propose Mechanism of Causation for Zofran-Related Heart Defects

Brian Finehout-Henry1 year ago

Researchers believe the congenital heart defects associated with Zofran could be caused by disrupted blood flow.

Zofran Increases the Risk of Birth Defects

Off-label use of Zofran in treating morning sickness during pregnancy has been associated with double the risk of cleft palate and double the risk of heart defects, according to reporting by the Toronto Star.

Zofran, which has the generic name ondansetron, was developed by GlaxoSmithKline and received FDA approval in 1991. The FDA label for Zofran says the drug has been approved to treat nausea and vomiting after surgery or arising from cancer treatment.

GlaxoSmithKline was investigated by the United States Department of Justice for illegal activities and court documents allege that GlaxoSmithKline: illegally marketed Zofran for treating morning sickness, distributed false information about the safety of Zofran, and paid doctors kickbacks for prescribing Zofran to pregnant women with morning sickness.

In 2012, the Department of Justice announced that GlaxoSmithKline would pay $3 billion and plead guilty to settle the fraud and withholding of safety information allegations associated with multiple drugs.

Zofran Doubles the Risk of Heart Birth Defects

A study in Reproductive Toxicology reports finding increased heart defects with Zofran used during pregnancy and suggests ondansetron could lead to heart defects because it disrupts the QT interval of the heart and causes heart arrhythmias.

The FDA has issued warnings about Zofran causing QT prolongations and heart arrhythmias. A study in Clinical Pharmacokinetics reports Zofran has been found to easily cross the placenta and can be found at high levels in fetal tissues.

The embryonic heart is the most susceptible to the effects of drugs, which alter the QT interval, of any hearts studied, according to research in Cardiovascular Research. An article in Teratology reports that pregnant animal studies have found that heart septal defects, holes in the heart, are easily produced when the fetus is exposed to QT altering drugs.

It is thought that the septal defects occur with QT altering drugs because of arrhythmias and disruption to blood flow and oxygen, according to research published in Reproductive Toxicology.

Early Pregnancy Use of Zofran Associated with Cleft Palate and Heart Defects

An article in American Journal of Obstetrics and Gynecology reports that over the last ten years the use of ondansetron, which is Zofran’s generic name, for treating morning sickness during pregnancy has increased dramatically.

The American College of Obstetricians and Gynecologists explain that morning sickness usually begins during the middle of the first trimester of pregnancy.

It is during the first trimester that the heart and palate are forming and developing and that the fetus is most susceptible to drug induced birth defects, according to Johns Hopkins Medicine.

The Centers for Disease Control and Prevention (CDC) explains that a cleft palate occurs when the tissues, which make up the roof of the mouth, fail to join together and that symptoms and complications include:

  • Feeding problems
  • Failing to grow properly
  • Hearing trouble
  • Problems speaking
  • Breathing difficulties

Treatments associated with cleft palate include include:

  • Multiple surgeries to repair the cleft
  • Surgeries to place ear tubes
  • Speech therapy
  • Special dental and orthodontist care

The Mayo Clinic explains that atrial septal defects, ventricular septal defects, and atrioventricular septal defects are holes in the walls separating the different chambers of the heart and can have the following symptoms, depending on severity:

  • Arrhythmias
  • Murmur
  • Stroke
  • Heart Failure
  • Difficulty feeding
  • Poor growth
  • Fatigue
  • Trouble breathing
  • Lung infections
  • Valve problems

Treatments for congenital heart defects can include:

  • Medical monitoring
  • Surgeries to repair the hole and/or valve
  • Medications


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