Haloperidol
Haldol
Butyrophenone antipsychotic — low-dose antiemetic
Dopamine D2 antagonist (CTZ) → antiemetic at low doses; antipsychotic/sedating at higher doses.
Indications
- •PONV prophylaxis/rescue (low dose)
- •Agitation/delirium (higher dose)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| PONV | 0.5–1 mg IV/IM | — |
| Agitation | 2–5 mg IM/IV, titrate | — |
Pharmacokinetics
Onset ~10–30 min IV. Long half-life ~18 h. Hepatic.
Side effects
- !QT prolongation → torsades (FDA warning for IV use — monitor)
- !Extrapyramidal symptoms/dystonia
- !Neuroleptic malignant syndrome (rare)
- !Sedation
Contraindications
- ×Long QT
- ×Parkinson disease / Lewy body dementia
- ×Concurrent QT-prolonging drugs
Clinical pearls
- ★Effective low-dose antiemetic (droperidol's cousin) — but IV use carries a QT/torsades warning; monitor ECG.
- ★Avoid in Parkinson disease (D2 blockade worsens it).
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.
- Granisetron
Blocks serotonin 5-HT3 receptors (central CTZ + peripheral vagal afferents). More selective + longer-acting than ondansetron.
- 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.
Browse all classes: /reference/drugs
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •Miller's Anesthesia, 9e
- •FDA package insert
