Ondansetron — Drug Monograph

Brand names: Zofran, Zuplenz

Drug class: Supportive Care Agent

Mechanism of Action

Selective serotonin 5-HT3 receptor antagonist. Blocks 5-HT3 receptors on vagal afferents in the GI tract and in the chemoreceptor trigger zone (CTZ) of the area postrema. Prevents acute and, to a lesser degree, delayed chemotherapy-induced nausea and vomiting (CINV).

FDA Indications

• Prevention of nausea and vomiting associated with highly and moderately emetogenic chemotherapy (initial and repeat courses)
• Prevention of postoperative nausea and vomiting (PONV)
• Prevention of radiation-induced nausea and vomiting

Common Side Effects

• Headache (most common; 9–27%)
• Constipation
• Diarrhea
• Fatigue/malaise
• Dizziness

Clinical Pearl

Ondansetron is the most widely used antiemetic in oncology and is the backbone of CINV prophylaxis for moderately and highly emetogenic regimens. For highly emetogenic chemotherapy (HEC), ASCO/NCCN guidelines require a 3-drug regimen (5-HT3 antagonist + NK1 antagonist + dexamethasone) or 4-drug regimen (add olanzapine). Ondansetron is highly effective for acute CINV (0–24 hours) but less effective for delayed CINV (24–120 hours) — this is where NK1 antagonists add critical value.

Related Therapies & Mechanisms

• Aprepitant (Emend) — Supportive Care Agent
• Avatrombopag (Doptelet) — Supportive Care Agent
• Darbepoetin Alfa (Aranesp) — Supportive Care Agent
• Defibrotide (Defitelio) — Supportive Care Agent