Antipsychotic Agents - Definition & Classification

Antipsychotics Agents (also known as neuroleptics) are drugs used to treat schizophrenia, psychosis, bipolar disorder, and related psychiatric conditions.
Antipsychotic Agents modify dopamine and serotonin pathways to manage psychotic symptoms.
They act primarily by blocking dopamine (D2) receptors, though newer agents affect serotonin and other receptors as well.

Typical Antipsychotics (First-Generation)
- These drugs primarily block dopamine D2 receptors and are associated with higher risk of extrapyramidal side effects (EPS).
- Phenothiazines
  - Chlorpromazine hydrochloride
  - Triflupromazine
  - Thioridazine hydrochloride
  - Piperacetazine hydrochloride
  - Promazine hydrochloride
  - Prochlorperazine maleate
  - Trifluoperazine hydrochloride
Atypical Antipsychotics (Second-Generation)
- These have broader receptor targets (e.g., D2 and 5-HT2A) and typically lower risk of EPS.
- Ring Analogues of Phenothiazines
  - Clozapine
  - Loxapine succinate
  - Chlorprothixene
  - Thiothixene
- Fluorobutyrophenones
  - Haloperidol
  - Droperidol
  - Risperidone (Note: Though structurally similar to butyrophenones, it is pharmacologically atypical)
- Beta Amino Ketones
  - Molindone hydrochloride
- Benzamides
  - Sulpiride

Category	Sub-Class	Mechanism of Action	Examples	Key Features / Notes
Typical Antipsychotics	A. Phenothiazines	Primarily block dopamine D2 receptors → ↓ positive symptoms (hallucinations, delusions)	Chlorpromazine HCl, Triflupromazine, Thioridazine HCl, Piperacetazine HCl, Promazine HCl, Prochlorperazine maleate, Trifluoperazine HCl	High risk of extrapyramidal side effects (EPS); sedation, anticholinergic effects common

Atypical Antipsychotics	B. Ring Analogues of Phenothiazines	Block D2 and 5-HT2A receptors (serotonin-dopamine antagonism)	Clozapine, Loxapine succinate, Chlorprothixene, Thiothixene	Lower EPS risk; effective for negative symptoms; Clozapine may cause agranulocytosis
	C. Fluorobutyrophenones	D2 antagonism (Haloperidol); 5-HT2A & D2 antagonism (Risperidone)	Haloperidol, Droperidol, Risperidone (pharmacologically atypical)	Haloperidol: potent with high EPS risk; Risperidone: fewer motor side effects
	D. Beta Amino Ketones	D2 antagonism; possible multiple mechanisms	Molindone HCl	Less commonly used; may have weight-neutral profile
	E. Benzamides	Selective D2/D3 receptor blockade, especially in limbic system	Sulpiride	Atypical profile with fewer motor effects; used in Europe and Asia