Study Notes: Ondansetron & Related Medications

Study Notes: Ondansetron & Related Medications

I. Overview

• Ondansetron, along with Granisetron and Dolasetron, is an antiemetic medication.

• Function: Inhibits nausea and vomiting.

II. Mechanism of Action

• Blocks serotonin (5-HT₃) receptors on the vagus nerve.

• Works both:

  • Centrally → blocking the solitary nucleus & area postrema.

  • Peripherally → blocking synaptic areas.

III. Side Effects

• Most important: Can cause serotonin syndrome.

  • Confusing point: Although it blocks serotonin receptors, it may still result in excess free serotonin (since it antagonizes receptors, secreted serotonin has nowhere to bind).

  • This does not occur with medications that block receptors at allosteric sites.

• Other side effects:

  • QT interval prolongation

  • Constipation

  • Headache

IV. Quiz

• Question: Prolongation of QT interval results in which condition?

• Answer: Torsades de Pointes