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Does zofran cause constipation?

Does Zofran cause constipation?

Zofran (ondansetron) is an antiemetic used to prevent nausea and vomiting from chemotherapy, radiation, and surgery. It belongs to the 5-HT3 receptor antagonist class, blocking serotonin in the brain’s vomiting center. It comes as orally disintegrating tablets, oral tablets, solution, and injection.

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In clinical trials, headache occurred in 24% of patients, and constipation in 9% of those taking 8 mg twice daily.

Managing constipation on Zofran

  • Stay well hydrated
  • Increase dietary fiber
  • Engage in regular physical activity
  • If severe or persistent, consult your provider about laxatives (polyethylene glycol, docusate sodium, senna)

Common side effects of Zofran

  • Headache (up to 24%)
  • Fatigue or drowsiness (up to 13%)
  • Constipation (up to 9%)
  • Diarrhea (up to 6%)
  • Dizziness, anxiety, malaise, fever, itching, rash

Serious side effects of Zofran

  • Abnormal heart rhythms (QT prolongation, torsades de pointes): symptoms include palpitations, chest pain, lightheadedness, fainting. Higher risk with heart disease, electrolyte imbalances, or heart failure.
  • Serotonin syndrome: risk increases when combined with other serotonergic drugs. Symptoms include agitation, hallucinations, rapid heart rate, fever, tremor, seizures.
  • Allergic reactions: rash, hives, facial or throat swelling, breathing difficulty.
  • Overdose: vision changes, lightheadedness, fainting, severe constipation, serotonin syndrome in children.

Use in pregnancy

Zofran is used off-label for nausea and vomiting of pregnancy. Studies have mixed results on safety; some show no harm, others suggest slight increased risk of cleft palate or heart defects when used in the first trimester. Discuss risks and benefits with your provider.

Sources

  • Ondansetron (Rx). Medscape. Accessed June 26, 2025.
  • Griddine A, Bush JS. Ondansetron. StatPearls. Updated Feb 15, 2023. Accessed June 26, 2025.
  • Huybrechts KF et al. Association of Maternal First-Trimester Ondansetron Use With Cardiac Malformations and Oral Clefts. JAMA. 2018;320(23):2429–2437. Accessed June 26, 2025.
  • Zambelli-Weiner A et al. First trimester ondansetron exposure and risk of structural birth defects. Reprod Toxicol. 2019;83:14–20. doi:10.1016/j.reprotox.2018.10.010. Accessed June 26, 2025.

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