Canonical Question
NeuroPharm – Anti-Depressants/Anti-Psychotics
Master answer
ANTI-PSYCHOTIC DRUGS
CLASSIFICATION
| TYPICAL Antipsychotic Agents | ATYPICAL Antipsychotic Agents | |
|---|---|---|
| (D2-R) | (D2-R<5-HT2a) | |
| Includes | (1) Phenothiazines (Eg. Chlorpromazine) (2) Butyrophenone (Eg. Haloperidol) (3) Thioxanthenes (Eg. Flupenthixole) | (1) Diazepines (Eg. Clozapine, Olanzapine) (2) Dibenzothiazepines (Eg. Quetiapine) (3) Benzamides (Eg. Sulpiride) (4) Benzisoxazols (Eg. Respirdone) |
| Mechanism of Action | (i) Primarily potent D2R antagonists (> 80% of receptors must be antagonised for therapeutic effect) (ii) Moderate antagonism of 5-HT2 receptors and α-adrenoceptor (iii) Weakly inhibit mAChR and H1R | (i) Highly selective D2R antagonists (> 80% of receptors must be antagonised for therapeutic effect) (ii) High affinity for 5-HT2R and moderate affinity for α-adrenoceptors (Except benzamides) (iii) Diazepines have D4R antagonistic effect also |
| Effect | Ameliorate +ve symptoms only (little effect on –ve symptoms) | Indicated for treatment resistance or side-effects with typical agents (esp extrapyramidal symptoms) Have greater therapeutic efficacy (ameliorate both +ve and –ve symptoms) |
| Side Effects | Very narrow TI – Substantial side-effects at therapeutic doses (i) Movement disorders: – Extrapyramidal symptoms, such as dystonias, akathisias, pseudoparkinsonism – These are acute and reversible – Tardive dyskinesia (involuntary movements of tongue, lips, face, trunk and extremities) – Gradual onset and irreversible (ii) Endocrine – Sexual dysfunction, gynaecomastia (due to PRL release), menstrual disorders, weight gain (iii) Hypotension (α-adrenoceptor-related) (iv) Sedation (H1R related) (v) Seizures (vi) Jaundice and agranulocytosis (esp with phenothiazines) (vii) Anticholinergic symptoms (viii) Neuroleptic malignant syndrome | fewer side effects than typical agents (esp movement disorders and gynaecomastia) (i) Cardiac arrhythmias (ii) seizures (iii) clozapine-induced agranulocytosis (requires blood screening) (iv) myocarditis and cardiomyopathy (requires cardiac enzyme and TTE monitoring) |
PHARMACOLOGY OF HALOPERIDOL
Exam appearances
| Exam | Exact wording | Relationship | Success |
|---|---|---|---|
| 2021B Q16 | Classify the anti-psychotic drugs (25% marks). Outline the pharmacology of haloperidol (75% marks). | historical_member | — |