Atypical Antipsychotics

Atypical Antipsychotics

1. Definition, scope & terminology

• Antipsychotic (neuroleptic, major tranquilliser, ataractic) drugs reduce psychotic symptoms across schizophrenia, bipolar disorder, psychotic depression, dementia/Parkinson's-disease psychosis, and drug-induced psychosis; they are symptomatic, not curative (KDT 8e Ch.32, pp.464, 472).
• Atypical = second-generation antipsychotic (SGA) — newer agents with weak D₂ blockade but potent 5-HT_2a antagonism, defined operationally by a low liability for extrapyramidal symptoms (EPS) at clinically effective doses (the original "atypicality" criterion, derived from clozapine) (G&G 14e Ch.19, p.364; KDT 8e Ch.32, p.468; Katzung 16e Ch.29, p.537).
• The term "neuroleptic" is reserved for chlorpromazine/haloperidol-type conventional agents — potent D₂ blockers that produce "psychic indifference," emotional quietening and EPS without ataxia or cognitive impairment; a neuroleptic is formally a subtype of antipsychotic that causes EPS at effective doses or catalepsy in animals (KDT 8e Ch.32, p.463; Katzung 16e Ch.29, p.537).
• Historical anchor: chlorpromazine introduced 1952 (the dawn of psychopharmacology); clozapine discovered 1959 and recognised by the mid-1960s to be antipsychotic with virtually no EPS — the dissociation of antipsychotic efficacy from EPS that founded the "atypical" class (KDT 8e Ch.32, p.462; Katzung 16e Ch.29, p.537; G&G 14e Ch.19, p.364).
• SGAs have largely replaced FGAs as first-line, chiefly for their more favourable neurological side-effect profile — not for superior antipsychotic efficacy (G&G 14e Ch.19, p.375; KDT 8e Ch.32, p.473).