First-generation antipsychotics

First-generation antipsychotics block dopamine D2 receptors. Blockade in the mesolimbic pathway suppresses hallucinations and delusions, and in the chemoreceptor trigger zone it stops vomiting; blockade in the basal ganglia causes extrapyramidal effects, and in the anterior pituitary it lifts dopamine's brake on prolactin. Low-potency drugs such as chlorpromazine also block α1, muscarinic and H1 receptors.

• HaloperidolHigh-potency: strong D2 block with little anticholinergic action, so movement effects are common; a decanoate depot is injected into muscle every 4 weeks.
• ChlorpromazineA low-potency phenothiazine with broad receptor block; beyond psychosis it treats severe nausea and intractable hiccups.

• Schizophrenia and other psychoses
• Mania in bipolar disorder
• Acute agitation in psychosis or mania
• Severe nausea and vomiting
• Tourette's syndrome and other tic disorders
• Intractable hiccups

• Dystonia and parkinsonism (extrapyramidal effects)Known for
• Tardive dyskinesia with long-term useKnown forSerious
• Raised prolactin: breast swelling, milk, missed periodsKnown for
• Akathisia (inner restlessness)
• Neuroleptic malignant syndromeSerious
• Drowsiness
• Dizziness on standing (orthostatic hypotension)
• QT prolongation and torsades de pointesSerious
• Low white cell count, even agranulocytosisSerious
• Higher death rate in older people with dementiaSerious

What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.

• Older people with dementia-related psychosis have a higher death rate on antipsychotics; the US labels do not approve them for it.
• D2 blockade worsens Parkinson's disease; haloperidol is contraindicated in it.
• Take care with QT-prolonging drugs, low potassium or magnesium, and heart disease.
• Stop at once and treat urgently if fever, muscle rigidity and confusion suggest neuroleptic malignant syndrome.

Written for biofideX in plain words, after checking these references:

• Treatment: schizophrenia (NHS)
• Antipsychotic Agent (NCI Thesaurus)
• Haloperidol 1 mg/ml oral solution: SmPC (emc)
• Chlorpromazine hydrochloride: label (DailyMed)

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.