Haloperidol (Haldol) | Medication Reference

Bedside Snapshot

High-potency typical antipsychotic used in ED/ICU primarily for acute agitation, delirium-associated severe distress, and refractory nausea/vomiting or hiccups. Strong D₂ blockade with minimal anticholinergic or hypotensive effect at usual doses, but higher risk for extrapyramidal symptoms (EPS) and QTc prolongation than many atypicals.

Common adult dosing for acute agitation/delirium (parenteral): 2.5–10 mg IM or IV initially, with repeat doses of 2.5–10 mg every 15–30 minutes as needed; many ED/ICU protocols cap single doses at 5–10 mg and total daily dose around 20–30 mg, using much lower doses (0.5–2 mg) in older or frail patients.

Elderly or medically fragile patients with delirium: Start low (0.5–1 mg PO/IV/IM), repeat every 30–60 minutes as needed, then convert to scheduled low-dose regimens (e.g., 0.5–1 mg q4–6h) with daily max often 5–10 mg depending on risk factors.

Onset (IM): Sedation and antipsychotic effects typically begin within 20–30 minutes, peak around 30–60 minutes; IV onset can be within 5–10 minutes with peak at 10–20 minutes. Duration of a single dose is often 4–8 hours, but half-life is much longer with repeated dosing.

IV haloperidol is widely used in ED/ICU practice but is technically off-label; major concerns are QTc prolongation and risk of torsades de pointes, especially with high IV doses, rapid IV push, electrolyte derangements, or other QT-prolonging drugs. Many institutions require ECG and electrolyte monitoring when cumulative IV doses exceed certain thresholds (e.g., >10–20 mg/day).

EPS (acute dystonia, akathisia, parkinsonism) are common dose-limiting side effects; prophylactic or rescue anticholinergics (e.g., diphenhydramine, benztropine) are often used when giving larger or repeated doses. Neuroleptic malignant syndrome (NMS) is rare but life-threatening.

Haloperidol decanoate is a long-acting IM depot formulation for chronic psychosis maintenance; it is not used for acute agitation or ICU delirium management.

Brand & Generic Names

Generic Name: Haloperidol
Brand Names: Haldol (oral, IM, IV; lactate and decanoate), multiple generics – availability is region- and institution-specific

Medication Class

Typical antipsychotic; high-potency butyrophenone; dopamine D₂ receptor antagonist

Pharmacology

Mechanism of Action:

Haloperidol is a high-potency typical antipsychotic of the butyrophenone class that exerts its primary effects by antagonism of dopamine D₂ receptors in the mesolimbic, mesocortical, and nigrostriatal pathways
D₂ receptor blockade in mesolimbic pathways is associated with antipsychotic and anti-delirium effects (reduced hallucinations, delusions, agitation)
Blockade of dopaminergic neurotransmission in the nigrostriatal pathway underlies the high risk for extrapyramidal symptoms, including acute dystonia, akathisia, parkinsonism, and tardive dyskinesia with chronic use
Haloperidol also has varying affinity for other receptors (e.g., D₁, α₁-adrenergic, and minimal muscarinic and histamine H₁ effects), contributing to modest orthostatic hypotension and sedation at higher doses but less anticholinergic burden than low-potency agents
QTc prolongation and torsades risk are thought to be related to blockade of cardiac IKr (hERG) potassium channels, especially at high plasma concentrations and with IV administration

Pharmacokinetics:

Formulations: Oral tablets/solution, short-acting IM/IV haloperidol lactate, and long-acting depot IM haloperidol decanoate
Onset: IV administration produces onset of effect within 5–10 minutes; IM onset is typically 20–30 minutes; oral onset is 30–60 minutes with peak at 2–6 hours
Duration: Single parenteral doses generally provide 4–8 hours of clinical effect, though sedative/antipsychotic effects may last longer with repeated dosing due to long elimination half-life
Distribution: Highly lipophilic with extensive tissue distribution; volume of distribution is large (on the order of 10–20 L/kg). Protein binding is ~90%
Metabolism: Primarily hepatic via CYP3A4 and CYP2D6 (oxidative metabolism and N-dealkylation) to inactive metabolites; subject to wide interindividual variability
Elimination: Elimination half-life after oral or parenteral dosing is typically 12–36 hours (longer with chronic use); depot haloperidol decanoate has an apparent half-life of several weeks
Hepatic impairment or strong CYP3A4/2D6 inhibition can substantially increase haloperidol exposure; dose reduction and close monitoring are recommended in such cases
Renal impairment has less effect on kinetics but uremia and associated physiology may alter CNS sensitivity and QTc risk

Dosing & Administration

Available Forms:

Oral tablets: commonly 0.5 mg, 1 mg, 2 mg, 5 mg, 10 mg, and sometimes higher strengths
Oral solution: e.g., 2 mg/mL haloperidol drops/solution
Short-acting injectable (lactate): typically 5 mg/mL haloperidol in 1 mL ampoules for IM or IV use (IV use is off-label in many regions)
Depot formulation (decanoate): 50 mg/mL or 100 mg/mL in oil for deep IM injection every 4 weeks or individualized maintenance intervals (not for acute agitation)

Dosing – Haloperidol for Acute Agitation and Delirium (Always Follow Local Protocols):

Indication / Population	Initial Dose & Route	Repeat / Titration	Notes
Adult acute agitation (ED/ICU, non-elderly, relatively healthy)	2.5–10 mg IM or IV	May repeat 2.5–10 mg every 15–30 minutes as needed	Many protocols cap total daily dose at ~20–30 mg; often combined with a benzodiazepine
Adult ICU delirium – hyperactive (scheduled/PRN)	0.5–2 mg IV/IM/PO	Every 2–4 hours as needed; may increase to 2–5 mg if insufficient response	Use lowest effective dose; reassess daily and wean as delirium improves
Elderly / frail patients with delirium or dementia-related agitation	0.25–0.5 mg PO/IV/IM	May repeat every 30–60 minutes, then schedule 0.25–0.5 mg q4–6h	Very sensitive to EPS and QTc prolongation; many protocols cap daily dose at 5–10 mg
Refractory nausea/vomiting or intractable hiccups – adult	0.5–2 mg PO/IV/IM	Every 4–6 hours as needed	Often effective at very low doses; monitor for EPS, especially akathisia
Pediatric agitation – specialist-directed	0.025–0.075 mg/kg PO/IM/IV (max 5 mg/dose)	Repeat per protocol; typically every 30–60 minutes as needed	Use pediatric psychiatry/toxicology guidance; higher EPS risk
Maximum daily dose (typical ED/ICU practice)	~20–30 mg/day IV/IM/PO for most adults	Lower maxima (5–10 mg/day) in elderly, QTc risk, or hepatic impairment	Some psychiatry regimens use higher doses orally; risk–benefit must be carefully weighed

Additional Dosing Notes:

IV use of haloperidol is off-label in many jurisdictions but widely practiced in ED/ICU settings; institutional policies may specify EKG monitoring and dose limits for IV use
Correct hypokalemia, hypomagnesemia, and bradycardia before and during IV haloperidol therapy when possible to reduce torsades risk
For patients with prolonged baseline QTc (e.g., >500 ms), congenital long QT, or taking multiple QT-prolonging drugs, consider alternative agents (e.g., atypical antipsychotics such as olanzapine, quetiapine, or non-antipsychotic options) and involve pharmacy/consult services
In severe agitation, combining haloperidol with a benzodiazepine (e.g., lorazepam) and/or an antihistamine (e.g., diphenhydramine) is common ("B52"–style regimens), but increases risk of oversedation and respiratory depression; continuous monitoring is essential

Contraindications

Contraindications:

Known hypersensitivity to haloperidol or other butyrophenones
Severe CNS depression or coma from any cause without airway protection
Parkinson's disease or Lewy body dementia (relative but strong caution) due to high sensitivity to D₂ blockade and risk of severe EPS and neuroleptic sensitivity reactions
Previous severe reaction to antipsychotics such as neuroleptic malignant syndrome (use with extreme caution, if at all)

Major Precautions:

QTc prolongation and torsades de pointes: Risk increased with IV use, high doses, rapid infusion, electrolyte abnormalities, bradycardia, and concurrent QT-prolonging drugs
Cardiovascular disease: Haloperidol can cause orthostatic hypotension, tachycardia, and arrhythmias; monitor closely in patients with structural heart disease, heart failure, or recent MI
Elderly patients with dementia-related psychosis: Antipsychotics (including haloperidol) carry an increased risk of death; use lowest effective dose for shortest duration and only when non-pharmacologic measures fail
Hepatic impairment: Reduced clearance and increased exposure; use lower doses and monitor closely
History of EPS or tardive dyskinesia: Haloperidol carries high EPS liability; consider atypical agents or non-dopamine-blocking strategies when feasible
Seizure disorders: Antipsychotics may lower seizure threshold; use cautiously in patients with epilepsy or recent head trauma

Adverse Effects

Common:

Sedation and somnolence
Extrapyramidal symptoms: Acute dystonia (e.g., torticollis, oculogyric crisis), akathisia, and parkinsonism
Restlessness, inner tension, or subjective agitation (akathisia)
Anticholinergic-type effects at higher doses: dry mouth, constipation, blurred vision (less than with low-potency agents)
Orthostatic hypotension and mild tachycardia

Serious:

Torsades de pointes and sudden cardiac death due to QTc prolongation, particularly with high-dose IV use and risk factors
Neuroleptic malignant syndrome (NMS): Fever, rigidity, autonomic instability, altered mental status, elevated CK; requires immediate discontinuation and intensive supportive care
Severe EPS, including laryngospasm, oculogyric crisis, and dystonic reactions, which may compromise airway; treat with anticholinergics (e.g., diphenhydramine or benztropine)
Tardive dyskinesia with chronic use: Involuntary choreoathetoid movements of face, tongue, or extremities, often irreversible
Severe hypersensitivity reactions (e.g., angioedema, anaphylaxis) – rare

Monitoring

Baseline and follow-up ECG (especially for IV or high-dose therapy) to monitor QTc; many institutions recommend continuous telemetry when using repeated IV doses
Vital signs (HR, BP, RR, SpO₂) and level of consciousness, particularly when combined with other sedatives or in medically ill patients
Signs and symptoms of EPS (dystonia, akathisia, parkinsonism) and prompt treatment with anticholinergics if they occur
Temperature, muscle rigidity, autonomic parameters, and mental status in patients on higher doses or multiple antipsychotics to detect early NMS
Electrolytes (K⁺, Mg²⁺) in patients at risk for QTc prolongation, and periodic monitoring in ICU patients receiving ongoing IV haloperidol
Daily reassessment of need for ongoing antipsychotic therapy in delirium; attempt taper/discontinuation as soon as clinically feasible

Indications / Clinical Uses (ED/ICU/Ward)

Acute agitation and aggression associated with delirium, dementia, psychosis, or intoxication when non-pharmacologic measures are insufficient and patient/staff safety is at risk
Management of hyperactive ICU delirium causing severe agitation, self-removal of lines/tubes, or interference with life-sustaining therapy (as part of a multimodal delirium protocol)
Adjunctive treatment of schizophrenia and acute psychosis (PO/IM, and decanoate for maintenance)
Treatment of severe refractory nausea and vomiting or intractable hiccups (off-label, low-dose haloperidol)

Clinical Pearls

Start low and go slow in the elderly: 0.25–0.5 mg doses of haloperidol can be surprisingly effective for delirium-related agitation in elderly and medically fragile populations.

Acute dystonia treatment: If a patient develops acute dystonia (e.g., oculogyric crisis, torticollis) after haloperidol, treat promptly with IV/IM diphenhydramine or benztropine—symptoms often resolve within minutes, and this can be very reassuring to staff and family.

ICU delirium multimodal approach: For hyperactive ICU delirium, haloperidol is often used PRN while non-pharmacologic strategies (reorientation, sleep-wake normalization, glasses/hearing aids, early mobilization) and treatment of underlying causes are prioritized.

Transition from bolus to scheduled dosing: When repeated IV doses are required, consider transitioning to scheduled low-dose oral or IV haloperidol and/or an atypical antipsychotic to reduce large bolus exposures and smooth plasma levels.

Avoid QT-prolonging drug stacking: Avoid stacking multiple QT-prolonging drugs (e.g., haloperidol + IV ondansetron + fluoroquinolones) in high-risk patients; involve pharmacy or cardiology for complex polypharmacy cases.

Haldol decanoate is not for acute use: Haldol decanoate is for chronic outpatient maintenance, not acute ED/ICU delirium—avoid using depot formulations for unstable or undiagnosed patients.

References

Lexicomp. (2025). Haloperidol: Drug information. Wolters Kluwer.
DrugBank Online. (2024). Haloperidol (DB00502). DrugBank. https://go.drugbank.com/drugs/DB00502
Devlin, J. W., Skrobik, Y., Gélinas, C., et al. (2018). Clinical practice guidelines for the prevention and management of pain, agitation/sedation, delirium, immobility, and sleep disruption in adult ICU patients. Critical Care Medicine, 46(9), e825–e873.
Riker, R. R., & Shehabi, Y. (2013). Delirium and sedation in the intensive care unit. New England Journal of Medicine, 369(5), 444–454.
EMCrit Project. (2024). Delirium & antipsychotics (IBCC). https://emcrit.org/ibcc/delirium/