Antiemetic

Ondansetron

5-HT3 receptor antagonist · Zofran

Mechanism: Blocks 5-HT3 receptors in CTZ and vagal afferents.

Calculate dose for your patient

Enter weight (kg or lb). Always verify before administration.

Patient weight

Computed weight

70.0 kg · 154.3 lb

PONV prophylaxis

3.5 mg – 7.0 mg

= 1.75–3.50 mL (2 mg/mL)

Exceeds typical adult max 4 mg — cap and reassess.

Adult: 4 mg IV at end of case.

Weight is saved on this device for the next calculator you open.

Full dose calculator

Onset

5–15 min

Duration

4–8 h

Metabolism

Hepatic CYP3A4.

Dosing

Adult

4 mg IV at end of case (prophylaxis); 4 mg IV q4–8 h (rescue).

Pediatric

0.1 mg/kg IV (max 4 mg).

Indications

PONV prevention/treatment
Chemotherapy-induced nausea

Contraindications

Long QT syndrome (relative; dose-dependent QT prolongation)

Side Effects

Headache
Constipation
QT prolongation

Clinical Pearls

1Most effective if given at end of case rather than at induction.

References & Further Reading

1
Textbook
Flood P, Rathmell JP, Shafer S. Stoelting's Pharmacology and Physiology in Anesthetic Practice. 5th ed. Philadelphia: Wolters Kluwer; 2015.
2
Journal
Apfel CC, Läärä E, Koivuranta M, Greim CA, Roewer N. A simplified risk score for predicting postoperative nausea and vomiting. Anesthesiology. 1999;91(3):693-700.
3
Journal
Apfel CC, Korttila K, Abdalla M, et al. A factorial trial of six interventions for the prevention of postoperative nausea and vomiting (IMPACT). N Engl J Med. 2004;350(24):2441-2451.
4
Textbook
Gropper MA, Miller RD, Cohen NH, et al., eds. Miller's Anesthesia. 9th ed. Philadelphia: Elsevier; 2020.
5
Textbook
Adriano A, Morris R, eds. 2021 CA-1 Tutorial Textbook (15th Ed.). Stanford University Medical Center, Department of Anesthesiology.

Citations are provided to direct further study. Always check the most current edition of guidelines and society recommendations — the information in this chapter is a teaching summary, not primary source material.