Granisetron
Kytril · Sustol
5-HT3 receptor antagonist antiemetic
Blocks serotonin 5-HT3 receptors (central CTZ + peripheral vagal afferents). More selective + longer-acting than ondansetron.
Indications
- •PONV prophylaxis/treatment
- •Chemotherapy/radiation-induced N/V
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| PONV | 0.35–1 mg IV near end of surgery | — |
Pharmacokinetics
Onset minutes IV. Longer half-life (~9 h) than ondansetron. Hepatic CYP3A4.
Side effects
- !Headache
- !Constipation
- !QT prolongation (class effect — less than ondansetron)
Contraindications
- ×Congenital long QT
- ×Concurrent strong QT-prolonging drugs
Clinical pearls
- ★Longer-acting 5-HT3 blocker — useful when you want durable PONV coverage.
- ★Class QT caution (generally less than ondansetron/dolasetron).
Other drugs in Antiemetics & Related
- Ondansetron
Blocks serotonin receptors at vagal afferents and chemoreceptor trigger zone.
- Metoclopramide
Central D2 antagonism at the chemoreceptor trigger zone (antiemetic). Peripherally, sensitizes upper-GI tissue to acetylcholine → increases lower esophageal sphincter tone, accelerates gastric emptying, speeds duodenal transit. Mild 5-HT4 agonism contributes to prokinesis.
- Droperidol
Potent central D2 antagonism at the chemoreceptor trigger zone. Also α-adrenergic blockade and mild GABA-A facilitation. Highly effective antiemetic and sedative — historically a key component of neuroleptanalgesia.
- Aprepitant
Selective antagonist at central neurokinin-1 receptors in the area postrema and nucleus tractus solitarius. Blocks substance-P-mediated emesis, particularly the delayed phase (24–72 h post-stimulus) where 5-HT3 antagonists lose efficacy.
- Dolasetron
5-HT3 antagonist (prodrug → hydrodolasetron). Effective antiemetic but the most QT/dysrhythmia-prone of the class.
- Promethazine
H1 antihistamine with anticholinergic + antidopaminergic activity → antiemetic + sedation + antihistamine effects.
- Haloperidol
Dopamine D2 antagonist (CTZ) → antiemetic at low doses; antipsychotic/sedating at higher doses.
Browse all classes: /reference/drugs
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •Miller's Anesthesia, 9e
- •FDA package insert
