Haloperidol (Haldol)

Emergency & Prehospital

• Severe agitation: use it when verbal de-escalation has failed and the patient, bystanders or staff are at risk. Effective alone or with lorazepam, but it is slower than droperidol or an atypical antipsychotic plus midazolam. IV use is off-label.
• Acute psychosis or mania with agitation: fast control when oral therapy is not appropriate. The US injection label covers schizophrenia.

ED / ICU / Transport

• Hyperactive delirium with distress or danger: short-term control of agitation, hallucinations or self-harm (pulling lines or tubes). Use it after the causes are treated and nonpharmacologic measures have failed (off-label in the US). Not for hypoactive delirium.
• Refractory nausea and vomiting: use it when first-line antiemetics have failed (off-label).
• Cannabinoid hyperemesis syndrome (CHS): it relieved nausea and abdominal pain better than ondansetron. Off-label.
• Postoperative nausea and vomiting (PONV): prophylaxis, or combination treatment, in moderate- to high-risk patients when other antiemetics fail. UK-labeled, off-label in the US.

Other Uses

• Schizophrenia and other psychotic disorders: oral and IM maintenance. Haloperidol decanoate is the 4-weekly depot.
• Tourette's disorder: oral haloperidol carries an FDA label for tics in children and adults.
• Huntington's disease chorea: IM, once other drugs have failed and oral therapy is not possible. UK-labeled.

Doses vary by protocol; follow local protocols and medical direction. Unless a dose is marked (UK label or guideline), it follows the FDA label. Where a current guideline disagrees, its dose goes first, and the label value stays visible.

Available Forms

• Haloperidol lactate injection (immediate release): 5 mg/mL in a 1 mL (5 mg) single-dose vial or 10 mL (50 mg) multiple-dose vial. The label covers IM use only, so IV is off-label. This is the one EDs, ICUs and EMS agencies carry.
• Haloperidol decanoate (long-acting depot): 50 mg/mL and 100 mg/mL in sesame oil, deep IM every 4 weeks for schizophrenia maintenance. Never give it IV. Never use it for acute agitation.
• Oral: tablets 0.5, 1, 2, 5, 10 and 20 mg; oral concentrate 2 mg/mL (as lactate).

Adult Dosing

Pediatric Dosing

Where does a pediatric dose come from? Three sources, in this order: AHA/AAP 2025 where it states a dose, then the NASEMSO National Model EMS Clinical Guidelines v3.0 (2022), then the US label. If none of them gives a dose, none is shown. A pediatric maximum never exceeds the adult maximum dose (NASEMSO Universal Care Guideline, p. 13). "Pediatric" here means up to 40 kg or 14 years, whichever comes first. Unless marked labeled, a pediatric dose is off-label.

Weight-based dose checks: pediatric weight-based dosing.

Preparation & Administration

• Check the product: confirm "haloperidol lactate 5 mg/mL" (immediate release) and not decanoate before drawing up. Inspect for particles and discoloration.
• IM: undiluted into a large muscle. That's the labeled route.
• IV (off-label): give only with continuous ECG monitoring for QTc prolongation and arrhythmias (US and UK labels). Torsades risk is highest at higher-than-recommended doses and with IV use.
• Before dosing when feasible: baseline ECG, and correct low K⁺ and Mg²⁺ (UK label). In dangerous agitation, the dose comes first. Get the ECG as soon as it is safe.
• Switch to oral: use the previous 24-hr parenteral total as the first estimate of the oral daily dose (US label; UK label: 1:1); first oral dose 12–24 hr after the last injection.

Contraindications

• US label: severe toxic CNS depression or coma from any cause; hypersensitivity (anaphylaxis, angioedema reported); Parkinson's disease; dementia with Lewy bodies
• UK label adds (relative in US practice): known QTc prolongation or congenital long QT syndrome; history of ventricular arrhythmia or torsades de pointes; recent acute myocardial infarction; uncompensated heart failure; uncorrected hypokalemia; other QT-prolonging drugs; progressive supranuclear palsy

Precautions

• QTc risk factors: low K⁺, Mg²⁺ or Ca²⁺, bradycardia, structural heart disease, hypothyroidism, heavy alcohol use, CYP2D6 poor metabolizers taking a CYP3A4 inhibitor.
• Seizure risk: it lowers the seizure threshold. Use caution in epilepsy, brain injury and alcohol withdrawal.
• Prior neuroleptic malignant syndrome (NMS): recurrence has been reported on re-exposure.
• Cardiovascular disease and hypotension: transient hypotension or angina may occur.
• Thyrotoxicosis: severe neurotoxicity, with rigidity and inability to walk or talk, has been reported.
• Older adults, dementia, stroke risk: higher mortality, cerebrovascular events and falls.

Hold / Reassess If

• QTc >500 ms: stop haloperidol (UK label); any QTc prolongation: reduce the dose
• K⁺ or Mg²⁺ low: correct before the next dose
• Restlessness rising after a dose (akathisia): do not escalate the dose
• Fever, rigidity or autonomic instability: stop and evaluate for NMS
• Over-sedation or falling SpO₂ with benzodiazepines or opioids on board: support the airway, hold further doses

Common

• Extrapyramidal symptoms (EPS): about 51% vs 16% with placebo in oral trials (Fresenius label, Table 1: 284 haloperidol, 282 placebo); tremor 8%, hypertonia 7%, dystonia 7%
• Akathisia and hyperkinesia: hyperkinesia about 10%; akathisia is subjective. The patient feels a distressing restlessness.
• Somnolence: about 5%
• Constipation and dry mouth: about 4% and 2%
• Orthostatic hypotension and tachycardia
• Hyperprolactinemia: galactorrhea, amenorrhea, gynecomastia with ongoing use

Serious / Life-Threatening

Overdose & Toxicity Management

• Signs: severe EPS (rigidity, tremor), hypotension, sedation progressing to coma with respiratory depression and shock; QTc prolongation and torsades. Hypertension has been reported in a 2-year-old.
• Immediate management: airway and ventilation; IV fluids, then norepinephrine or phenylephrine for hypotension (no epinephrine); anticholinergic for severe EPS; continuous ECG until it normalizes.
• Antidote: none specific. Treat torsades with magnesium and defibrillation; call Poison Control (1-800-222-1222).
• Extracorporeal removal: dialysis is not recommended. It removes very little haloperidol.

Clinically Significant Interactions

IV Compatibility

• Labeling: US and UK haloperidol lactate products are labeled for IM use. Their labels give no IV diluent or Y-site data.
• Practice: flush the line before and after an IV push; do not mix in a syringe or line with other drugs unless your compatibility reference confirms it.
• Decanoate: it is an oil-based depot. Never IV.
• Verify with an institutional compatibility resource.

• Pediatrics: Injection safety and effectiveness in children are not established (US and UK labels). Oral haloperidol is labeled from age 3 yr. Younger patients get acute dystonia more often. EPS risk climbs above 3 mg/day, and IV dosing carries a very high EPS risk. Agitation dosing lives in the Pediatric Dosing table (NASEMSO 2022: 1–3 mg IM, age 6–12 yr; the 2019 BETA consensus differs). See also weight-based dosing.
• Neonates: Not used. Third-trimester exposure can cause neonatal EPS or withdrawal. Watch for agitation, abnormal tone, tremor, respiratory distress and feeding problems. Tell the neonatal team.
• Pregnancy: There are no well-controlled human studies. Still, more than 400 exposed pregnancies show no malformative or fetal/neonatal toxicity signal (UK label). Limb malformations were reported with first-trimester use, alongside other possibly teratogenic drugs, and no cause was proven. Animal studies: resorption and pup mortality, but no malformations in rats or rabbits. Cleft palate appeared in mice at about 0.1 times the maximum human dose (US label). The UK label advises avoiding use in pregnancy as a precaution. The US label advises use only when the benefit justifies the potential risk, such as dangerous agitation.
• Lactation: It passes into breast milk. The US label advises against breastfeeding during treatment. For a short exposure, talk it through with a pharmacist or lactation resource.
• Older Adults: The boxed warning for dementia-related psychosis applies here. Start at half the lowest adult dose. The UK label caps the dose at 5 mg/day. Tardive dyskinesia, falls and stroke all occur at higher rates. The AGS Beers Criteria list antipsychotics as potentially inappropriate in older adults.
• Renal Impairment: No dose adjustment is recommended, but use caution (UK label). Less than 3% is excreted unchanged. In severe impairment, consider a lower initial dose, then titrate to response, because haloperidol and its reduced metabolite have long half-lives and may accumulate (UK label). Dialysis does not remove it.
• Hepatic Impairment: The liver does most of the clearing, so halve the initial dose and titrate to response (UK label).
• Obesity / Dosing Weight: Adult doses don't scale with weight. The drug is lipophilic and spreads widely, with a volume of distribution of 8–21 L/kg. Pediatric per-kg doses stop at the adult-range caps.
• Parkinson's Disease, Lewy Body Dementia, Progressive Supranuclear Palsy: Expect severe EPS, confusion and falls. Contraindicated (PSP: UK label only). Pick a strategy that doesn't block dopamine.
• CYP2D6 Poor Metabolizers: Levels run higher. Use caution, especially with a CYP3A4 inhibitor.

• Scope: Carried by paramedic, RN and critical-care transport teams where it is stocked, for behavioral emergencies (Paramedic/RN/CCT). It varies by state and agency protocol. ACEP 2024 makes no recommendation for or against specific agents out of hospital.
• Storage & Stability: 20–25°C (68–77°F); protect from light; do not freeze. Keep vials in the carton. Don't leave them where the vehicle heats up or chills down.
• Carried Concentration: haloperidol lactate 5 mg/mL (5 mg = 1 mL). Decanoate vials (50 or 100 mg/mL) look similar on a shelf, but they are a depot product. Read the label aloud before drawing up.
• Monitoring After Chemical Sedation: continuous SpO₂, cardiac monitor and EtCO₂ when combined with a benzodiazepine; reassess vital signs, airway and tone often. Check glucose and look for hypoxia, head injury, intoxication or withdrawal.
• Interfacility Transport: confirm the 24-hr total haloperidol dose, latest QTc and electrolytes, and any other QT-prolonging drugs before departure; bring diphenhydramine for dystonia.
• Handoff Essentials: time, dose and route of each dose (mg), total mg in 24 hr, other sedatives given, response, restraint use, ECG or QTc, EPS signs and temperature.

Mechanism of Action

• It blocks central dopamine D₂ receptors (mesolimbic). The result is less psychosis and agitation.
• Blocking D₂ in the nigrostriatal pathway causes EPS (dystonia, akathisia, parkinsonism). With long use, it leads to tardive dyskinesia.
• Blocking D₂ in the chemoreceptor trigger zone gives the antiemetic effect. Blocking it in the pituitary causes hyperprolactinemia.
• Weaker α₁-adrenergic binding causes orthostatic hypotension. Minimal muscarinic and H₁ binding means little anticholinergic effect.
• QTc prolongation rises with dose and concentration, and torsades risk is highest with IV and high doses.

Pharmacokinetics

• Half-life: on average 21 hr (range 13–36 hr) after IM dosing. It runs longer in older adults. Decanoate: about 3 weeks.
• Metabolism: the liver breaks it down along several routes: glucuronidation, ketone reduction (to reduced haloperidol, which may convert back) and CYP3A4 and CYP2D6 oxidation. Haloperidol inhibits CYP2D6.
• Elimination: about 33% in urine and 21% in feces after IV dosing; less than 3% unchanged in urine.
• Absorption and distribution: IM absorption is complete. Oral bioavailability is 40–75% (first-pass). Protein binding is 88–92%, and volume of distribution is 8–21 L/kg. It crosses the blood-brain barrier and the placenta.

Generic Name

Haloperidol (tablets); haloperidol lactate (immediate-release injection, oral concentrate); haloperidol decanoate (depot injection)

Brand Names

Haldol (historical brand; current US injectable and oral products, including the decanoate, are marketed generically)

Pharmacologic Class

Butyrophenone; dopamine D₂ receptor antagonist

Therapeutic Class

First-generation (typical) antipsychotic; antiemetic (off-label)

Controlled Substance

Not controlled

ISMP High-Alert

No

Look-Alike / Sound-Alike

None on the ISMP confused-names list. Product mix-up risk: haloperidol lactate (immediate release, 5 mg/mL) vs haloperidol decanoate (depot, 50 or 100 mg/mL)