granisetron
Brand: Kytril, Sancuso, Sustol
Prototype: ondansetron
Drug Class: 5-HT3 receptor antagonist
Drug Family: antiemetic
Subclass: second-generation serotonin antagonist antiemetic
Organ Systems: gastrointestinal
Mechanism of Action
Selectively antagonizes 5-HT3 receptors on vagal afferents in the GI tract and in the chemoreceptor trigger zone, blocking serotonin-mediated emetic signaling triggered by chemotherapy, radiation, and surgery.
5-HT3 receptors (vagal afferents, CTZ, GI tract)
Indications
- chemotherapy-induced nausea and vomiting (CINV)
- postoperative nausea and vomiting (PONV)
- radiation-induced nausea and vomiting
Contraindications
- hypersensitivity to granisetron
Adverse Effects
Common
- headache
- constipation
- asthenia
- injection site reactions (IV)
Serious
- QT prolongation
- serotonin syndrome (with other serotonergic agents)
- hypersensitivity reactions
Pharmacokinetics (ADME)
| Absorption | oral bioavailability ~60%; transdermal patch (Sancuso) and extended-release SC injection (Sustol) also available |
| Distribution | 65% protein bound; widely distributed |
| Metabolism | hepatic via CYP3A4 |
| Excretion | renal (12%) and fecal (48%) |
| Half-life | 3–14 hours (IV); up to 10 days (Sustol extended-release) |
| Onset | 30–60 minutes |
| Peak | variable by route |
| Duration | 24 hours |
| Protein Binding | 65% |
| Vd | 3 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| QT-prolonging agents | additive QT prolongation risk | major |
| serotonergic drugs | serotonin syndrome risk | major |
| ketoconazole | CYP3A4 inhibition increases granisetron levels | moderate |
Nursing Considerations
- Administer IV granisetron 30 minutes before chemotherapy; oral form given 1 hour before chemo.
- Monitor ECG in patients with cardiac disease or on other QT-prolonging medications.
- The Sancuso transdermal patch is applied 24–48 hours before chemotherapy and worn for up to 7 days.
- Educate patients that constipation is a common side effect; recommend adequate fluid intake and fiber.
Clinical Pearls
- Granisetron has a longer half-life than ondansetron, allowing once-daily dosing for CINV prophylaxis.
- The Sustol extended-release subcutaneous formulation maintains therapeutic levels for 5 days post-injection, ideal for multi-day chemotherapy regimens.
Safety Profile
Pregnancy generally-safe
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.