Pharmacology · First-generation antipsychotics

Haloperidol !

A high-potency classic antipsychotic that strongly blocks dopamine D2 receptors. Used for psychosis, agitation and Tourette's tics.

Updated 2026-11-01

Class: First-generation antipsychotics
Receptor: Dopamine D2 receptor
ATC code: N05AD01
WHO Model List of Essential Medicines

Dopamine D2 receptorHaloperidol

The figure shows haloperidol in the human D2 receptor (fused to a lysozyme for crystallisation).

Target in 3D: Dopamine D2 receptor. PDB structure 6LUQ (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Haloperidol is a butyrophenone that blocks D2 receptors with high affinity and has little action on muscarinic, histamine or α1 receptors. It controls positive psychotic symptoms and agitation and suppresses tics, but its strong striatal D2 blockade makes extrapyramidal effects common. It also raises prolactin.

Haloperidol blocks D2 receptors with high affinity
Mesolimbic D2 block: fewer hallucinations and delusions
Striatal D2 block: extrapyramidal effects
Pituitary D2 block: prolactin rises

Pharmacokinetics

Absorption: Given by mouth or by intramuscular injection; a long-acting decanoate injection also exists
Metabolism: Liver metabolism; enzyme inducers such as rifampicin and carbamazepine lower its levels
Elimination: Slow elimination, so antiparkinson drugs may be needed for a while after it is stopped

Indications

Psychotic disorders such as schizophrenia
Tics and vocal utterances of Tourette's disorder
Acute agitation in psychosis (intramuscular form)

Adverse effects

Common

Acute dystonia, akathisia and drug-induced parkinsonism
High prolactin: breast enlargement, galactorrhoea, menstrual changes, sexual dysfunction
Sedation (less than low-potency drugs)

Contraindications

Parkinson's disease
Severe central nervous system depression or coma
Hypersensitivity to haloperidol

Key interactions

Lithium: Rare encephalopathic syndrome (weakness, fever, confusion, extrapyramidal signs), sometimes with lasting brain damage
Rifampicin or carbamazepine: Much lower haloperidol levels and loss of effect
Other QT-prolonging drugs, low potassium or magnesium: Higher risk of torsades de pointes

What is monitored

ECG when given intravenously or with QT risk factors
Electrolytes (potassium, magnesium)
Abnormal movements at each visit
Blood count if fever or infection appears

Administration and safety

The short-acting injection (lactate) is not approved for intravenous use; if given IV, the ECG is monitored for QT prolongation
The short-acting lactate injection and the long-acting decanoate injection are different products and are not interchangeable

Nursing care

Watches for fever, rigidity and confusion (neuroleptic malignant syndrome) and for abnormal movements; reports them at once
Has an anticholinergic or diphenhydramine order ready for acute dystonia (neck, jaw or eye spasm)
Checks the ECG and electrolytes in patients with heart disease or QT-prolonging drugs
Teaches the patient to avoid overheating and dehydration, and to avoid alcohol and other sedatives

Pregnancy and breastfeeding

Newborns exposed in the third trimester may have extrapyramidal or withdrawal symptoms (agitation, abnormal tone, tremor, feeding problems); use weighs benefit and risk.

Test yourself

Think of the answer, then tap the question to see it.

Why is haloperidol contraindicated in Parkinson's disease?

It blocks striatal D2 receptors, which are already short of dopamine, and worsens the motor symptoms.

Which cardiac risk rises when haloperidol is given intravenously or at high doses?

QT prolongation with torsades de pointes and sudden death.

A young man develops a painful neck twist hours after a haloperidol injection. What is it and how is it treated?

Acute dystonia; it responds quickly to an anticholinergic such as benztropine, or to diphenhydramine.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - HALOPERIDOL tablet (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - HALOPERIDOL- haloperidol lactate injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Haloperidol: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 19 (McGraw Hill, 2023).

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Representative model, for educational purposes only.