Pharmacology · First-generation antipsychotics
Chlorpromazine !
The first antipsychotic, a low-potency phenothiazine: very sedating, lowers blood pressure, also controls nausea and hiccups.
Updated 2026-11-01
The figure shows haloperidol in the human D2 receptor; chlorpromazine blocks the same binding site (no chlorpromazine-bound human D2 structure exists).
Mechanism of action
Chlorpromazine blocks D2 receptors with lower potency than haloperidol and also blocks H1, α1 and muscarinic receptors. This mix explains its strong sedation, orthostatic hypotension and anticholinergic effects, and fewer (but still possible) extrapyramidal effects. Dopamine blockade in the chemoreceptor trigger zone makes it antiemetic.
- Chlorpromazine blocks D2, H1, α1 and muscarinic receptors
- D2 block: less psychosis, less nausea and vomiting
- H1 and α1 block: sedation and orthostatic hypotension
- Muscarinic block: dry mouth, constipation, blurred vision
Pharmacokinetics
- Absorption
- Given by mouth or by injection
- Metabolism
- Extensive liver metabolism; it inhibits CYP2D6
Indications
- Schizophrenia and other psychotic disorders
- Nausea and vomiting
- Intractable hiccups
- Manic episodes of bipolar disorder
- Adjunct in tetanus and acute intermittent porphyria
Adverse effects
Common
- Marked sedation
- Orthostatic hypotension and falls
- Dry mouth, constipation, urinary retention, blurred vision
- Photosensitivity
- Lens and corneal deposits with long use
Contraindications
- Hypersensitivity to phenothiazines
- Coma or large amounts of CNS depressants (alcohol, barbiturates, opioids)
Key interactions
- Adrenaline (epinephrine)
- Paradoxical further fall in blood pressure; noradrenaline or phenylephrine are used instead
- Alcohol and other sedatives
- Additive sedation and hypotension
- Thiazide diuretics
- More orthostatic hypotension
- Chemotherapy
- Its antiemetic effect can hide vomiting as a sign of drug toxicity
What is monitored
- Blood pressure lying and standing
- Blood count if sore throat or fever appears
- Liver tests if jaundice appears
- Abnormal movements
Administration and safety
- Look-alike name: «chlorproMAZINE» is written with tall-man letters on labels to avoid mix-ups with similar names
- If hypotension needs a vasopressor, noradrenaline or phenylephrine are used, not adrenaline
Nursing care
- Checks lying and standing blood pressure and helps the patient stand up slowly (orthostatic hypotension, falls)
- Teaches sun protection (photosensitivity)
- Asks the patient to report sore throat, fever or yellow skin at once
- Watches for fever, rigidity and confusion (neuroleptic malignant syndrome) and for abnormal movements; reports them at once
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 does chlorpromazine cause orthostatic hypotension?
It blocks α1-adrenergic receptors on blood vessels, so they cannot constrict normally when the patient stands up.
Why is adrenaline avoided to treat chlorpromazine-induced hypotension?
With α1 blocked, adrenaline's β2 vasodilator action dominates and blood pressure can fall further.
Which non-psychiatric uses of chlorpromazine are classic exam facts?
Nausea and vomiting, intractable hiccups, and as an adjunct in tetanus and acute intermittent porphyria.
Related drugs
← Back to the class: First-generation antipsychotics
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 - CHLORPROMAZINE HYDROCHLORIDE tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Chlorpromazine: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 19 (McGraw Hill, 2023).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.