Droperidol
Inapsine
Butyrophenone D2 receptor antagonist
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.
Indications
- •PONV prophylaxis (high-efficacy, low-cost — equivalent to ondansetron in randomized trials)
- •Acute agitation in ED / postop
- •Migraine refractory to other agents
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| PONV prophylaxis | 0.625–1.25 mg IV at induction or end of case | 0.01–0.015 mg/kg IV (max 0.1 mg/kg/24 h) |
| PONV rescue | 0.625 mg IV q4–6 h prn | — |
Pharmacokinetics
Onset 3–10 min IV. Peak 30 min. Duration 2–4 h. Hepatic metabolism + renal excretion.
Hemodynamic effects
α-blockade can cause hypotension, especially in volume-depleted patients. Minimal HR effect.
Respiratory effects
Minimal at antiemetic doses; potentiates opioid respiratory depression at higher (anesthesia) doses.
Side effects
- !QT prolongation → torsades — boxed warning (FDA 2001)
- !Extrapyramidal symptoms (akathisia, dystonia) — less than metoclopramide
- !Sedation
- !Hypotension
- !Neuroleptic malignant syndrome (rare)
Contraindications
- ×Known or suspected QT prolongation (baseline QTc > 440 men, > 450 women)
- ×Hypokalemia / hypomagnesemia uncorrected
- ×Concomitant Class I or III antiarrhythmics
- ×Pheochromocytoma
Clinical pearls
- ★QT BOXED WARNING (2001): driven by 273 case reports including 74 deaths over 3 decades — but the 0.625-1.25 mg PONV dose has not been clearly linked to torsades; risk concentrated in older >5 mg neuroleptic doses. ASA still endorses low-dose use.
- ★EFFICACY: at 0.625-1.25 mg IV, equivalent to 4 mg ondansetron with 1/10 the cost. Reasonable first-line with a normal QT.
- ★AVOID: combining with other QT-prolongers (ondansetron, methadone, haloperidol) without checking QTc.
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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.
- 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.
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