NEUROLEPTICS
NEUROLEPTICS
- Also known as “Antipsychotics”.
- Mainstay of treatment for schizophrenia, schizoaffective disorders & delusional disorders.
Classification:
- Typical antipsychotics/1st generation antipsychotics/dopamine receptor antagonists (DRAs).
- Atypical antipsychotics/2nd generation antipsychotics/serotonin-dopamine antagonists.
TYPICAL ANTIPSYCHOTICS:
- MOA: Mainly act through dopamine, D2 receptor antagonism in mesolimbic tract.
Actions:
- Effective against positive symptoms.
- Minimal effect on negative symptoms.
Sub-classifications:
According to chemical groups –
- Phenothiazines: Chlorpromazine, Thioridazine, Trifluoperazine, Prochlorperazine, Triflupromazine, Fluphenazine, Perphenazine.
- Thioxanthenes: Thiothixene, flupenthixol.
- BuUrophenonesi Haloperidol, droperidol, penfluridol.
- Miscellaneous: Pimozide, loxapine, molindone.
According to potency –
- Low potency – Chlorpromazine & thioridazine.
- High potency – Haloperidol & fluphenazine.
Side effects:
- Movement disorders – Extrapyramidal symptoms (acute dystonia, acute akathisia, drug-induced parkinsonism, tardive dyskinesia, neuroleptic malignant syndrome, hyperprolactinemia, sedation, orthostatic hypotension & anticholinergic side effects.
ATYPICAL ANTIPSYCHOTICS:
MOA:
- Act through antagonism of 5Ht-2 receptors & D2 receptors.
- Higher ratio of 5 HT2 to D2 blockade.
Actions:
- Effective in treatment of both positive & negative symptoms.
- Lesser risk of causing extrapyramidal side effects as well as hyperprolactinemia – Due to lesser D2 blockade.
Drugs included –
- Clozapine, Olanzapine, Risperidone, Paliperidon, Iloperidone, Quetiapine, Ziprasidone, Aripiprazol, Sertindole, Zotepine, Lurasidone, Asenapine & Amisulpride
Side effects –
- Movement disorder – Lesser incidence.
- Hyperprolactinemia – Lesser incidence.
- Weight gain.
- Increased risk of dyslipidemia, diabetes & cardiovascular disease.
- Sedation, QTc prolongation (especially with ziprasidone).
- Seizures.
Important points on antipsychotics:
- Long-acting injectable antipsychotics (Depot anti-psychotics):
- Used in poorly compliant patients.
- IM injection once a month/fortnight.
Durgs:
- Flupenthixol, Fluphenazine, Haloperidol, Pipotiazine, Zuclopenthixol, Risperidone, Olanzapine, Paliperidone & Aripiprazole.
Thioridazine:
- Cause irreversible retinal pigmentatlon.
- Cause cardiac arrhythmias (prolongation of QT interval)
- Drug with least extrapyramidal side effects (Among typical antipsychotics).
Chlorpromazine:
- Cause corneal & lenticular deposits.
Penfluridol:
- Longest acting antipsychotic.
Ziprasidone:
- Cause cardiac arrhythmias (prolongation of QT interval)
Aripiprazole:
- Partial agonist at D2 receptors
- (all other antipsychotics are D2 antagonists).
Exam Important
- Neuroleptics are also known as “Antipsychotics”.
- Antipsychotics are mainstay of treatment for schizophrenia, schizoaffective disorders & delusional disorders.
- Typical antipsychotics mainly acts through dopamine, D2 receptor antagonism in mesolimbic tract.
- Extrapyramidal symptoms (acute dystonia, acute akathisia, drug-induced parkinsonism, tardive dyskinesia, neuroleptic malignant syndrome, hyperprolactinemia, sedation, orthostatic hypotension & anticholinergic side effects are all most important side effects associated with typical antipsychotics.
- Atypical antipsychotics act via antagonism of 5Ht-2 receptors & D2 receptors.
- Lesser risk of extrapyramidal side effects & hyperprolactinemia is observed with atypical antipsychotics due to lesser D2 blockade.
- Lesser incidence of movement disorder & hyperprolactinemia is seen with atypical antipsychotics.
- Long-acting injectable antipsychotics (Depot anti-psychotics) are used in poorly compliant patients.
- Thioridazine causes irreversible retinal pigmentation & cardiac arrhythmias.
- Chlorpromazine causes corneal & lenticular deposits.
- Penfluridol is longest acting antipsychotic.
- Ziprasidone cause cardiac arrhythmias
- Aripiprazole is a partial agonist at D2 receptors (all other antipsychotics are D2 antagonists).
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