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5-HT3 antagonist

Ondansetron

ZofranOndansetrona

How it works

Blocks serotonin (5-HT3) receptors in the chemoreceptor trigger zone. Prevents both acute and delayed nausea/vomiting.

Backbone antiemetic for chemo. Give on schedule (not as-needed) for best efficacy. Max 8 mg per dose (QT risk at > 16 mg/day). Add olanzapine or aprepitant for breakthrough nausea per MASCC/ESMO 2023.

Dosing

Typical doses

  • 4–8 mg PO BD–TID
  • 8 mg IV on chemo day

Schedule

  • D1–D3 of chemo cycle (scheduled, not PRN)
    cycle_linked

Side Effects

  • Headache
  • Constipation (opioid-like effect on bowel)
  • Dizziness, lightheadedness
  • QT prolongation (rare, usually benign)