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Anti-Psychotics - Coggle Diagram
Anti-Psychotics
Overview
They competitively block D2 receptors; not curative, only alleviates psychotic symptoms by decreasing intensity of hallucinations & delusions
Schizophrenia
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Characterized by delusions, hallucinations (in form of voices) & thinking or speech disturbances**
Caused by some inherent brain dysfunction in mesolimbic or mesocortical dopaminergic neuronal pathways
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A type of psychosis, a chronic & disabling mental disorder
Causes of schizophrenia
**Overstimulation of D2 receptors in brain mesolimbic pathway - causes +ve symptoms including hallucination & delusions
Dysfunction/hypofunction of D1 receptors in brain mesocortical pathways - causes -ve symptoms (poverty of speech & thought, apathy, reduced social drive, loss of motivation)
Used for treating
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Mania with psychotic symptoms (grandiosity, paranoia, hallucination & delirium)
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Classification
SECOND GENERATION
(1) Aripiprazole (2) Asenapine (3) Clozapine (4) Olanzapine (5) Quetiapine (6) Iloperidone (7) Lurasidone (8) Paliperidone
(9) Risperidone (10) Ziprasidone
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Effects
Anti-emetic
Most anti-psychotics (except aripiprazole) have anti-emetic effects mediated by blocking of D2 receptors of chemoreceptor trigger zone of medulla (eg: prochlorperazine)
Anti-cholinergic
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Peripheral anti-cholinergic effect such as: (1) blurred vision (2) dry mouth (except clozapine which increase salivation)
(3) inhibition of GI & urinary tract smooth muscle, leading to constipation & urinary retention
Some anti-psychotics produce anti-cholinergic effects:
(1) Thioridazine & chlorpromazine [1st gen]
(2) Clozapine & olanzapine [2nd gen]
EPS
Caused by blockage of dopamine receptors in nigrostriatal pathway (involves in voluntary motor control)
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Anti-psychotic
"-ve" symptoms - not responsive to 1st gen but many 2nd gen such as clozapine improve these -ve symptoms to some extent
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Adverse Effects
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Other effects
Lowered BP & orthostatic hypotension - for those anti-psychotics with a-adrenergic receptors blocking activity (eg: 1st gen chlorpromazine)
Depression of hypothalamus - causes many effects (affects thermoregulation [poikilothermia], amenorrhea, galactorrhea, gynecomastia, infertility, impotence)
Anti-cholinergic effects (dry mouth, urinary retention, constipation) for those anti-psychotic agents with potent anti-cholinergic activity (eg: 1st gen chlorpromazine, thioridazine)
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Drowsiness - occur due to CNS depression & anti-histaminic effects (eg: 1st gen chlorpromazine), usually during 1st few weeks of treatment
EPS
Blocking dopamine receptors alters this balance, causing relative excess of cholinergic influence, results in extrapyramidal motor effects
Generally, inhibitory effects of dopaminergic neuron are normally balanced by excitatory actions of cholinergic neurons in striatum
Appearance of EPS are time & dose-dependent
~dystonia (may occur after few hours to days)
~akathisias (may appear after days to weeks)
~parkinsonism (develop after weeks to months)
~tardive dyskinesia (can be irreversible, occur after months or years post-administration)
If cholinergic activity is blocked (by anticholinergic drug benztropine), EPS are minimized (dystonia) but parkinsonism symptoms & akathisias may persist
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Generations of Drug
1st Gen Anti-Psychotics
Competitive inhibitors at various receptors, but their anti-psychotic effects relies on competitive blocking of D2 receptors => alleviate schizophrenia symptoms
Usually associated with extra-pyramidal symptoms (EPS) - [dystonia, akathisia, parkinsonism & tardive dyskinesia]; Nigrostriatal dopaminergic pathway regulates extrapyramidal tracts (involved with motor planning). Blocking of dopamine receptor with anti-psychotics cause motor control impairment
Known as conventional, typical or traditional anti-psychotics
2nd Gen Anti-Psychotics
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However, usage is limited to refractory patients only due to serious side effects (eg: bone marrow suppression, seizures, CV side effects [HPT & tachycardia]) & risk of severe agranulocytosis (necessitates frequent monitoring of WBC counts)
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Pharmacokinetics
Some anti-psychotics - long-acting injectable (LA) formulations - administered via intramuscular (deep gluteal or deltoid)
= therapeutic duration of action: 2-4 weeks
= often used to treat outpatients & individuals who are non-compliant to oral medications
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