Granisetron

• Type: Antiemetic (prevents nausea/vomiting)

• Drug Class: 5-HT3 receptor antagonist (serotonin antagonist)

• Forms: Available as oral tablets, transdermal patch, and intravenous (IV) injection

How It Works

• Granisetron selectively blocks 5-HT3 receptors located in:

  • The vagus nerve in the gut

  • The chemoreceptor trigger zone (CTZ) in the brain

• By blocking serotonin signaling in these areas, it prevents nausea and vomiting caused by chemotherapy, radiotherapy, or surgery.

Common Uses

Granisetron is widely used to:

• Prevent chemotherapy-induced nausea and vomiting (CINV) – especially with highly emetogenic chemotherapy

• Prevent postoperative nausea and vomiting (PONV)

• Prevent nausea from radiotherapy

Advantages

• Highly selective → fewer side effects compared to older antiemetics

• Long duration of action (can cover delayed nausea when given as patch or extended infusion)

• Can be used in combination with dexamethasone or NK1 receptor antagonists for better nausea control

Possible Side Effects

Common:

• Headache

• Constipation

• Mild fatigue or dizziness

Less Common but Important:

• QT interval prolongation (risk of abnormal heart rhythms)

• Hypersensitivity reactions (rare)

Precautions

• Use with caution in patients with cardiac arrhythmias or prolonged QT interval

• Monitor for constipation in patients at risk of bowel obstruction

• Safe for most patients, including pediatric and elderly populations, with dose adjustments