Ondansetron in the Field
Objective: Ondansetron is for nausea and vomiting, after you have thought about ACS, low sugar, head injury, and other causes. There is a QT caution. The card has the amount.
Why this matters
Ondansetron is for nausea and vomiting. It can lower the chance of aspiration and make transport possible. It is not a diagnosis.
Think about the cause first. Inferior ST elevation and a head injury both cause vomiting. Low sugar does too. The drug is appropriate when the protocol says so. The card has the amount. This site does not list milligrams.
- Get a 12-lead if this could be ACS. Check glucose if this could be hypoglycemia.
- An oral dissolving tablet versus an IV dose is a packaging choice. This site does not list milligrams.
- Other antiemetics and some psychiatric medicines also prolong the QT interval. That combination is a caution. Follow your protocol.
Clinical sequence
- Think about the cause before you treat the symptom. Get a 12-lead if this could be ACS. Check glucose if this could be low sugar. A head injury still causes vomiting. So do other causes.
- Give ondansetron if the protocol includes it and the patient needs it to protect the airway and make transport possible. An oral dissolving tablet versus IV is a packaging choice. This site does not list milligrams.
- Respect the QT caution. Ondansetron can prolong the QT interval. Other antiemetics and some psychiatric medicines add QT risk. Follow the protocol. If the patient is actively vomiting, turn them and suction before a tablet.
Teaching points
- Use: nausea or vomiting, to protect the airway and make transport possible.
- Not a substitute for turning the patient, suction, or treating shock.
- QT: ondansetron can prolong the QT interval. A history of unstable dysrhythmia, or many QT-prolonging drugs, means follow the protocol or call online medical control.
- Children: many systems use it. Follow the pediatric protocol, not an adult memory.
Common errors
- Ondansetron instead of a 12-lead in a sweating patient with epigastric pain.
- Combining QT-prolonging drugs without checking the caution.
- Calling the call finished because the vomiting stopped.
Practice
One-minute check
With a partner: (1) isolated motion sickness and a clear story; (2) sweating and epigastric vomiting. For each, say whether the 12-lead or ondansetron comes first, and why.
Related: STEMI, Abdominal pain.
Sources & Further Study
Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.
- NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language. Your protocol still decides.
- FDA ondansetron QT safety communication — QT caution. Your protocol decides whether and how you give it.
- FDA labeling includes a QT caution. Follow your antiemetic protocol.
Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.
Check Your Understanding
Questions drawn only from this lesson. After you check, the key is highlighted. Education practice — not a certification exam.