Antipsychotic Medications

Antipsychotic medications are a class of psychotropic drugs whose primary shared action is blockade of dopamine D2 receptors and which are used to reduce psychotic symptoms such as hallucinations and delusions. They are conventionally divided into first-generation (typical) and second-generation (atypical) agents that differ in receptor profile and side-effect patterns.

Definition

Antipsychotic agents are drugs that reduce psychotic symptoms primarily through antagonism (or partial agonism) at dopamine D2 receptors, with secondary actions at serotonergic and other receptors that distinguish individual agents and generations.

Scope

This entry covers the antipsychotic drug class as a pharmacological topic: its mechanism of action, the typical/atypical distinction, the comparative efficacy and tolerability evidence from network meta-analyses, and the broad categories of adverse effects. It describes the class at a conceptual level and is reference-educational; it does not provide dosing or individualised treatment guidance.

Core questions

• What pharmacological action is shared across the class and how do typical and atypical agents differ?
• How do individual antipsychotics compare in efficacy and tolerability according to network meta-analyses?
• What broad categories of adverse effect (extrapyramidal, metabolic, and others) characterise the class?

Key concepts

• Dopamine D2 receptor blockade
• First-generation (typical) agents
• Second-generation (atypical) agents
• Extrapyramidal side effects
• Metabolic side effects
• Comparative efficacy and tolerability
• Treatment resistance and clozapine

Key theories

Dopamine D2 blockade as common mechanism

The antipsychotic effect across agents is attributed chiefly to antagonism at dopamine D2 receptors, consistent with the dopamine hypothesis of psychosis, with the degree and kinetics of D2 occupancy relating to both efficacy and motor side effects.

Mechanisms

The defining mechanism of the class is reduction of dopaminergic signalling, principally through D2 receptor antagonism, which counters the dopamine dysregulation linked to positive psychotic symptoms in the dopamine hypothesis described by Howes and Kapur. Atypical agents additionally engage serotonin and other receptors, a profile associated with a different balance of motor and metabolic effects compared with typical agents.

Clinical relevance

Antipsychotics are central to how psychotic disorders are managed, and the comparative evidence on their effects shapes the interpretation of treatment research. This entry summarises the class and its evidence base for educational reference; it is explicitly not prescriptive and does not address dosing or individual treatment selection.

Evidence & guidelines

Network meta-analyses by Leucht and colleagues (2013) compared the efficacy and tolerability of fifteen antipsychotics, and Pillinger and colleagues (2020) compared metabolic effects across eighteen agents, together informing the trade-offs between symptom control and side-effect burden. Correll and colleagues (2017) appraised the meta-analytic evidence on add-on (cotreatment) strategies.

History

The class began with the introduction of chlorpromazine in the early 1950s, which demonstrated that a drug could specifically reduce psychotic symptoms and launched modern psychopharmacology. Later development of clozapine and other second-generation agents broadened the receptor profiles available and reframed debates over the relative advantages of typical and atypical drugs.

Debates

Are second-generation antipsychotics genuinely superior to first-generation agents?

Network meta-analyses show that antipsychotics differ more by side-effect profile than by large, uniform efficacy gaps between generations, challenging a simple typical-versus-atypical dichotomy and emphasising drug-by-drug trade-offs.

Key figures

• Stefan Leucht
• Oliver Howes

Seminal works

• leucht-2013
• pillinger-2020
• howes-2009

Frequently asked questions

What is the main difference between typical and atypical antipsychotics?

Both reduce psychotic symptoms mainly through dopamine D2 receptor blockade, but atypical (second-generation) agents have additional receptor actions, notably at serotonin receptors. In comparative evidence the two groups differ more in their side-effect profiles - for example extrapyramidal versus metabolic effects - than in a uniform efficacy gap.

How do antipsychotics reduce psychotic symptoms?

Their shared action is to dampen dopamine signalling, primarily by blocking dopamine D2 receptors, which counters the dopamine dysregulation associated with positive symptoms such as hallucinations and delusions.