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Liquid ondansetron at triage showed no benefit over placebo for reducing observation time in pediatric gastroenteritisOndansetron at Triage Doesn’t Speed ER Discharge for Kids

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Key Takeaway
Note that ondansetron at triage showed no benefit over placebo in this underpowered study.

This randomized controlled trial evaluated liquid ondansetron versus a color- and taste-matched placebo in a tertiary pediatric ED in Canada. The population included 91 children aged 6 months to 17 years presenting with more than 3 episodes of vomiting in the preceding 24 hours, including at least one within 2 hours of arrival. Recruitment stopped prematurely due to the COVID-19 pandemic, and the study was underpowered.

The primary outcome measured the proportion of patients requiring observation after the first physician evaluation. Overall, 40 patients (45%) were discharged immediately. The absolute difference between groups was -1% (95% CI: -20% to 19%), indicating no significant difference between ondansetron and placebo groups (44% vs 45%). Secondary outcomes included post-intervention vomiting, ED length of stay, patient comfort, and 48-hour return visits.

Safety data were not reported for adverse events, serious adverse events, discontinuations, or tolerability. The study limitations include the premature cessation of recruitment and insufficient power to detect differences. Consequently, the efficacy of ondansetron when initiated at triage remains unclear.

This evidence could inform researchers planning larger clinical trials but does not currently support routine use based on these results.

  • Giving anti-vomiting medicine early didn’t reduce ER observation time
  • Helps kids with severe vomiting from stomach infections
  • Not ready for use—study too small to confirm results

This changes how we think about treating vomiting in kids at emergency rooms.

It starts with a fever. Then comes the vomiting. For parents, few things are more stressful than holding a sick child who can’t keep anything down. You rush to the ER, hoping for fast help. But what if treatment could start before seeing the doctor?

That’s the idea behind a new study testing whether giving medicine right at check-in helps kids leave the ER faster.

Vomiting from stomach bugs is one of the top reasons kids go to the emergency room. Most cases are from acute gastroenteritis — an infection that causes vomiting and diarrhea. It spreads easily, especially in schools and daycare centers.

While most kids get better on their own, some get dehydrated. That means they need IV fluids and hours of observation. For families, that means long waits, missed work, and stress.

Right now, doctors often give a medicine called ondansetron after evaluating the child. It helps stop vomiting. That can prevent IVs and hospital stays. But what if we gave it sooner?

The surprising shift

For years, experts thought early ondansetron might speed recovery. Some clinics already give it quickly — even before seeing a doctor.

But here’s the twist: this study tested whether giving it at triage — the very start of the ER visit — actually helps kids go home faster.

Researchers believed it would. After all, stopping vomiting early should mean less need for observation.

But the results didn’t match the hope.

What scientists didn’t expect

The study assigned kids to get either ondansetron or a fake pill (placebo) as soon as they arrived. Nurses gave the medicine before the doctor even saw them.

The goal? To see if early treatment reduced the number of children who needed to stay for monitoring.

But there was no real difference.

About 44% of kids getting ondansetron were sent home right after seeing the doctor. The same was true for 45% in the placebo group.

That means giving the medicine early didn’t change outcomes.

It’s not how the drug works

Ondansetron still works. It blocks signals in the gut and brain that cause vomiting. Think of it like a switch that turns off nausea.

But here’s the catch: just because the drug can stop vomiting doesn’t mean giving it earlier speeds up discharge.

Doctors still need to check for dehydration, fever, and other risks. Even if a child stops vomiting, they might still need fluids or observation.

It’s like fixing a car’s warning light — the light goes off, but the engine might still have problems.

This doesn’t mean this treatment is available yet.

The trial took place in a children’s ER in Canada. It included kids from 6 months to 17 years old. All had vomited at least three times in the past day — including once within two hours of arrival.

Ninety-one children joined: 44 got ondansetron, 47 got placebo. The medicine was given by nurses at triage, before any doctor visit.

Researchers then tracked who needed to stay for observation and who could go home right away.

Only 40 of the 91 kids (about 45%) were discharged immediately after the doctor’s first check. There was almost no difference between groups.

The ondansetron group had 44% sent home. The placebo group had 45%. That tiny gap could easily be due to chance.

No differences were seen in vomiting after treatment, how long kids stayed in the ER, comfort levels, or return visits within 48 hours.

In short: early ondansetron didn’t improve any key outcomes.

But there’s a catch.

The study was supposed to include over 200 kids. But it stopped early — because of the pandemic. Hospitals shut down non-urgent research. Recruitment ended with less than half the planned patients.

That means the study was too small to detect small but real benefits.

It’s like trying to hear a whisper in a loud room — the signal might be there, but the noise drowns it out.

The bigger picture

This result doesn’t mean ondansetron is useless. Other studies show it helps reduce vomiting and IV use when given later in care.

But this trial suggests timing matters. Giving it before assessment may not add extra benefit.

Experts say it highlights how complex ER care is. Just speeding up one step doesn’t always change the final outcome.

If your child is vomiting, don’t expect ERs to start giving anti-nausea medicine right away. This approach isn’t standard — and this study doesn’t support it.

Ondansetron is still used in many ERs, but usually after a doctor’s check.

Talk to your pediatrician about managing stomach bugs at home. Focus on small sips of fluids, rest, and watching for signs of dehydration.

Small study, big uncertainty

The main weakness? The trial was too small. With only 91 kids, it lacked the power to spot small differences.

Also, it was done at a single hospital. Results might differ elsewhere.

And since it was stopped early, we can’t be sure what a full study would have found.

What happens next

Researchers may restart this trial when conditions allow. A larger study could give clearer answers.

Until then, this serves as a caution: even smart ideas need solid proof.

Speeding up treatment sounds good. But real-world care depends on more than just one drug at one moment.

Study Details

Study typeRct
Sample sizen = 44
EvidenceLevel 2
PublishedApr 2026
View Original Abstract ↓
Objectives: Acute gastroenteritis is a leading cause of pediatric emergency department (ED) visits. While ondansetron reduces vomiting, intravenous rehydration, and hospital admissions, its efficacy when initiated at triage remains unclear. We aimed to evaluate whether triage nurse-initiated administration of ondansetron in children with suspected gastroenteritis reduces the proportion of patients requiring observation following initial physician assessment. Methods: We conducted a randomized, double-blind, placebo-controlled trial in a tertiary pediatric ED in Canada. Children aged 6 months to 17 years presenting with morae than 3 episodes of vomiting in the preceding 24 hours (including 1 within 2 hours of arrival), were eligible. At triage, we randomized participants to receive liquid ondansetron or a color- and taste-matched placebo. The primary outcome was the proportion of patients requiring observation after the first physician evaluation. Secondary outcomes included post-intervention vomiting, ED length of stay, patient comfort, and 48-hour return visits. The trial was registered at ClinicalTrials.gov (NCT03052361). Results: Recruitment was stopped prematurely due to the COVID-19 pandemic. Ninety-one participants were randomized to ondansetron (n= 44) or placebo (n= 47). Overall, 40 patients (45%) were discharged immediately after the initial physician assessment, with no difference between the ondansetron and placebo groups (44% vs. 45%; absolute difference -1%, 95% CI: -20% to 19%). No significant differences were observed in all secondary outcomes. Conclusion: In this trial, triage nurse-initiated ondansetron administration did not reduce the need for ED observation in children with presumed gastroenteritis. While being underpowered, this study could inform researchers planning larger clinical trials.
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