Report palpitations, syncope, dizziness, or an irregular heartbeat (QT prolongation/torsades).
Before you read
Test yourself first: 3 questions
Question 1 of 3
A client receiving ondansetron for nausea has a history of a prolonged QT interval. The nurse should:
Answer: B. Ondansetron can prolong the QT interval and risk dysrhythmias — monitor the ECG/electrolytes and report a known prolonged QT to the provider before giving.
Question 2 of 3
A client is receiving ondansetron for chemotherapy-induced nausea. Which is an expected therapeutic effect of this medication?
Answer: A. Ondansetron is a serotonin (5-HT3) receptor antagonist that prevents and relieves nausea and vomiting associated with chemotherapy. It is not used to raise blood counts, treat pain, or stimulate appetite as its primary action.
Question 3 of 3
A client receiving chemotherapy develops nausea and vomiting. The provider prescribes ondansetron. The nurse explains that this medication works by which mechanism?
Answer: B. Ondansetron is a serotonin (5-HT3) receptor antagonist that blocks serotonin at the chemoreceptor trigger zone and in the GI tract, preventing chemotherapy-induced nausea and vomiting. It does not coat the stomach, increase gastric pH, or stimulate motility.
Keep the streak going with more questions like these, each with a full rationale.
What is ondansetron?
It blocks serotonin both centrally in the chemoreceptor trigger zone and peripherally in the GI tract. Memory aid: the -setron suffix marks the 5-HT3 antiemetics.
Key points to remember
- Prevents and treats nausea/vomiting by blocking 5-HT3 serotonin receptors.
- Prolongs the QT interval and can cause life-threatening dysrhythmias such as torsades de pointes.
- Headache and constipation are the most common side effects.
- Can contribute to serotonin syndrome when combined with SSRIs, SNRIs, or other serotonergic drugs.
- Available as IV, oral tablet, and orally disintegrating tablet (ODT).
- Give before chemotherapy or anesthesia for prophylaxis rather than waiting for vomiting.
Signs & symptoms
- Headache, constipation, dizziness
Nursing priorities
- Obtain a baseline ECG/QT interval and electrolytes in at-risk patients.
- Monitor potassium and magnesium and correct deficits to lower dysrhythmia risk.
- Assess for relief of nausea/vomiting and monitor hydration status.
- Handle ODT with dry hands and place on the tongue to dissolve without water.
- Watch for signs of serotonin syndrome when given with other serotonergic agents.
Labs & values
Patient teaching
- Report fainting, chest fluttering, or a fast/irregular heartbeat right away.
- Increase fluids and fiber to prevent constipation.
- Tell your provider all medications, especially antidepressants.
- Take antiemetic before activities or treatments that trigger nausea when possible.
Red flags: report now
- Report palpitations, syncope, dizziness, or an irregular heartbeat (QT prolongation/torsades).
- Report agitation, fever, tremor, sweating, or hyperreflexia suggesting serotonin syndrome.
- Hold and report in patients with congenital long QT syndrome or uncorrected hypokalemia/hypomagnesemia.
References
Clinical references for this topic
