IMPORTANT! Updated June 16, 2020
In Summary, for those who received the ondansetron:

Benefits in NNT

  • 80.0% saw no benefit
  • 20.0% were helped by preventing vomiting
  • 100% saw no benefit for avoiding admission
  • 1 in 5 were helped (vomiting stopped)
  • 1 in 6 were helped (IV hydration avoided)
  • None were helped (avoiding admission)

Harms in NNT

  • 0% were harmed by medication side effects
  • None were harmed (medication side effect)

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Source: Federowicz Z, et al. Antiemetics for reducing vomiting related to acute gastroenteritis in children and adolescents (Review). Cochrane Database of Systematic Reviews 2011, Issue 9. Art.No.: CD005506. DOI: 10.1002/14651858.CD005506.pub5.
Decamp LR et. al. Use of Antiemetic Agents in Acute Gastroenteritis: A systematic review and meta-analysis. Arch Pediatr Adolesc Med. 2008 Sep;162(9):858-65.
U.S. Food and Drug Administration: FDA Drug Safety Communication: Abnormal heart rhythms may be associated with use of Zofran (ondansetron)

Efficacy Endpoints: Cessation of emesis, hospitalization, IV rehydration, readmission to ED within a 72 hour period.

Harm Endpoints: Medication side effects [diarrhea]

Narrative: Three studies examined administration of weight based oral ondansetron vs a placebo, totaling 465 patients. Included were children under the age of 18 who presented with vomiting and a clinical diagnosis of gastroenteritis. Excluded were children who were suffering from the effects of general anesthesia, chemotherapy, surgical conditions, metabolic disorders, and systemic infections.

The mainstay of gastroenteritis treatment in the ED involves rehydration, preferably through oral means. The studies demonstrated a reduction in IV rehydration rates) (RR 0.57, NNT 6, 95% CI 4 to 13) and an increase in cessation of vomiting (RR 1.34, NNT 5, 95% CI 3 to 7).

Caveats: In general the evidence quality for the involved trials was noted to be low to mid grade, and while the total number of subjects was just over one thousand, most outcome measure comparisons reported in these reviews included fewer than fiver hundred subjects total, making the confidence intervals wide and the findings somewhat less robust. Ondansetron appears to reduce vomiting among children with gastroenteritis. Whether the drug reduces hospital admission rates appears controversial. While the Cochrane review suggests an immediate admission benefit, a statistically similar proportion of children was admitted by 72 hours, suggesting that ondansetron only delayed rather than avoided hospital admission. If this is true it would not be considered a patient-oriented benefit and we have thus chosen not to list this as a benefit.

A number of studies reported an increase in diarrhea in the ondansetron group. Because of varying use of endpoints and outcome measures this could not be quantified, but did appear to be a fairly consistent finding. In addition, theFDA has issued a warning for increased QT (and potential Torsades) associated with ondansetron use, although the frequency and danger of this are unknown, and no study reported any cardiac effects, apparent arrhythmia events, or unexplained sudden deaths

The original manuscript was published in Medicine by the Numbers, American Family Physician as part of the partnership between and AFP.

Author: Nadim Lalani, MD and Damjan Gaco MD

Published/Updated: April 28, 2012

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
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