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Zofran Side Effects

Zofran (ondansetron) is an anti-nausea medication that was developed and approved to treat the side effects of chemotherapy and surgery. Doctors have also prescribed Zofran to treat morning sickness in pregnant women, an “off-label” use for the medication, as Zofran was never formally approved as safe for this purpose.  Studies have highlighted Zofran side effects, which include birth defects such as kidney and heart defects, cleft lip and/or palate, and poor fetal growth, as well as fetal death. One study suggest that the rate of such side effects may be as high as 30%.

Zofran overview

The drug Zofran was approved for use in the United States in 1991 after it was developed by the pharmaceutical company GlaxoSmithKline.  The FDA specifically approved Zofran for the treatment of nausea in chemotherapy and surgery patients.  Chemotherapy, radiation treatment, and surgery can trigger the release of a substance called serotonin in the digestive system which sends messages to a center in the brain that controls nausea and vomiting.  Zofran works by blocking serotonin receptors and preventing or mitigating nausea and vomiting for chemotherapy, radiation, and surgery patients.  Zofran can be given to adults and children (with some age restrictions for very young children) who are undergoing these treatments.  It can be administered in the form of tablets, syrup, intramuscular or intravenous injection, IV drip, or suppository.

Zofran side effects noted on the safety label include:

  • Rash, hives, itching, difficulty breathing (all of which may indicate an allergic reaction)
  • Blurred vision or temporary loss of sight
  • Slow heart rate
  • Anxiety or agitation
  • Breathing problems
  • Shivering
  • Feeling like you might faint
  • Disruption or change in urination

Patients who experience these side effects should seek prompt medical attention.  Other possible reactions include:

  • Drowsiness
  • Dizziness
  • Fatigue or weakness
  • Fever
  • Diarrhea or constipation
  • Headache

Off-label treatment for severe “morning sickness”

The FDA has never approved Zofran for the treatment of morning sickness experienced by many women during pregnancy.  Though some pregnant women have these symptoms in a relatively mild form, a small group of women (about 1%) suffer from hypermesis gravidarum, an extreme form of morning sickness that can involve constant vomiting, dehydration, nutritional deficiencies, and other side effects that can put mother and developing baby at risk.  In these  cases, doctors have sometimes prescribed Zofran as a treatment, especially when others have not been effective.

Heart complications linked to Zofran

Zofran can have a number of possible side effects, some more serious than others.  One of the most dangerous side effects involves the development of severe form of irregular heartbeat in connection with a fatal condition known as Torsade de pointes. The condition is difficult to detect and, if left untreated, it can involve increasingly severe episodes in which the brain is deprived of oxygen, ultimately resulting in severe brain damage or death.  

The FDA issued a safety warning concerning this rare, but serious condition in September of 2011. At this time, they ordered that Zofran’s label be updated to discourage the use of the drug in patients previously disposed to problems with irregular heartbeat.  In December of 2012, following a study by GlaxoSmithKline that was published the previous summer, the FDA issued a recall of the 32-mg intravenous (IV) dose of Zofran due to the risk of developing Torsade de pointes.  

Possible side effects experienced by Zofran patients that may point to heart problems include: 

  • Dizziness, light-headedness, or fainting
  • Shortness of breath
  • Fatigue
  • Palpitations
  • Pain or a sensation of pounding in the chest .

Zofran side effects for pregnant women

The use of Zofran has been connected to serious side effects for pregnant women and the children they carry.  In March 2013, the FDA expressed concern about the link between Zofran and serotonin syndrome in pregnant women.  Serotonin syndrome has symptoms that include mental and behavioral alterations, rapid heartbeat, high fever, loss of consciousness, seizures and other symptoms.  This potentially fatal syndrome may occur in women who are already taking antidepressants known as SSRIs (selective serotonin reuptake inhibitors).

Studies explore risks of Zofran during pregnancy

Zofran is a “Pregnancy Category B” medication: when tested on animals, the medication seems to be safe; however, it is not clear that it is safe for pregnant humans and their children.  This issue has been debated in the past as some major studies once suggested that Zofran was safe in this context.

For instance, a February 2013 study published in The New England Journal of Medicine declared the medication safe and unlikely to cause birth defects.  The study followed almost 2,000 women who took Zofran while pregnant between 2004 and 2011 and whose pregnancy health outcomes were recorded in a registry in Denmark.  However, not long after, researchers did a more comprehensive analysis of more women from the same registry over a longer period and found that Zofran did in fact have an impact on the risk of birth defects. Further debate and study continues today.

Birth defects alleged in Zofran lawsuits

Studies indicate that Zofran can pass from the mother to the fetus through the placental barrier, particularly during the first trimester of pregnancy.  In the second Danish study, which analyzed the outcomes of over 900,000 pregnant women who used Zofran, researchers found an overall increase in birth defects of about 30%.

In addition, according to the Star report, one child was born with a “musculoskeletal abnormality.”  In another case, a child was born with a mouth deformation, jaundice, heart murmur and two other serious heart defects.  The FDA has not made a specific pronouncement about the link between Zofran and birth defects. However, the agency has never approved the drug for use during pregnancy.

A recently filed lawsuit alleges that Zofran was responsible for multiple birth defects suffered by the plaintiff’s child, including several heart defects, facial deformities, low set ears, hearing problems, sensitivity to light, inguinal hernia, and webbed toes.  The child in question has required 10 surgeries in her 12 years of life to repair the defects.

  1. WebMD, Zofran

  2. Netdoctor, Zofran

  3. FDA, FDA Drug Safety Communication: New information regarding QT prolongation with ondansetron (Zofran)

  4. FDA, Potential Signals of Serious Risks/New Safety Information Identified by the FDA Adverse Event Reporting System (FAERS) between January– March 2013

  5. The Toronto Star, Birth Defects Blamed on Unapproved Morning Sickness Treatment

  6. OBGYN News, Ondansetron: New and troubling data

  7. United States Department of Justice, GlaxoSmithKline to Plead Guilty and Pay$3 Billion to Resolve Fraud Allegations and Failure to Report Safety Data,