antipsicóticos - resumo
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7/23/2019 Antipsicóticos - Resumo
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Antipsychotics (neuroleptics)
The dopamine hypothesis of psychosis:• Psychotic symptoms result from ! dopamine neurotransmission• Dopamine receptors:
o D1-like:! D1 and D5
! Are post-synaptic! Stimulate adenylate cyclase and ! cAMP
o D2-like:! D2, D3 and D4
! Are both pre- and post-synaptic! Inhibit adenylate cyclase and " cAMP
• Dopaminergic pathways:o Mesolimbic / mesocortical:
! Concerned with mood and emotional stability! Ventral tegmental area:
• Ventral striatum and the frontal cortexo Nigrostriatal:
! Concerned with movement! Substantia nigra and the dorsal striatum
• Neuroleptics block D2 receptors:o Explains why they cause movement disorders as a side effect
Clinical classification of neuroleptics:• Typical:
o Produce extrapyramidal symptoms (EPS)• Atypical:
o So-called because they have a low incidence of EPSo However, all apart from clozapine can cause EPS at high doses
Chemical classification of neuroleptics:• Typical:
o Phenothiazines:! Propylamines (chlorpromazine):
• Sedation ++• Anticholinergic ++• EPS ++
! Piperidines (thioridazine):• Sedation ++• Anticholinergic ++• EPS +• Can cause torsade de pointes
! Piperazines (fluphenazine):• Sedation +• Anticholinergic +• EPS +++
o Thioxanthines (flupenthixole):! Sedation +
! Anticholinergic +! EPS ++
o Butyrophenones (haloperidol):! Sedation -! Anticholinergic -! EPS +++
• Atypical:o “True”:
! Clozapine:• Sedation ++• Anticholinergic +• EPS -
o “Apparent”:! Sulpiride:
• Sedation +• Anticholinergic –• EPS +
! Risperidone:• Sedation ++• Anticholinergic +• EPS +
General effects of the neuroleptics:• Early (hours):
o Desired:! Sedation (histamine / #-receptor blockade)! Tranquilisation (dopamine blockade)
o Unwanted:! Acute dystonic reactions
• Medium (days–weeks):o Desired:
! Suppression of:• Delusions• Disordered thinking• Hallucinations
o Unwanted:! Akathisia! Parkinsonism
• Late (months–years):o Desired:
! Prevention of relapseo Unwanted:
! Tardive dyskinesia• Any time:
o Neuroleptic malignant syndromeChlorpromazine:
• Indications:o Psychotic disorders (e.g. schizophrenia / mania)o Labyrinthine disorders / vertigo
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o Nausea / vomitingo Chronic hiccups
• Adverse effects:o Common:
! Sedation! Anticholinergic effects:
• Blurred vision• Dry mouth• Postural hypotension• Constipation• Urinary retention
! Extrapyramidal effects:• Acute dystonia• Akathisia• Parkinsonism• Tardive dyskinesia
! Hyperprolactinaemia:• Amenorrhoea• Galactorrhoea• Impotence
o Uncommon:! Neuroleptic malignant syndrome! Agranulocytosis! Cholestatic jaundice
•
Interactions:o ACE inhibitors:
! Can cause severe hypotension
Haloperidol:• Indications:
o Psychosiso Motor tics
• Adverse effects:o Common:
! Extrapyramidal effects:• Acute dystonia• Akathisia• Parkinsonism
! Postural hypotensiono Uncommon:
! Convulsions! Neuroleptic malignant syndrome! Tardive dyskinesia! Weight loss
• Interactions:o Amiodarone:
! ! risk of ventricular arrhythmiaso Carbamazepine:
! " plasma levels of haloperidol (metabolism accelerated)
o Fluoxetine:! ! plasma levels of haloperidol
Clozapine:• Regarded by many as the only “true” atypical neuroleptic:
o EPS is not evident even at high doseso Effective in patients refractory to other neurolepticso Can treat the negative symptoms of schizophrenia
• Mechanism of action:o Blocks D4 and 5-HT2 receptorso Weak blockade of striatal D2 receptors
• Adverse effects:o Agranulocytosis (requires regular blood monitoring)o Myocarditis / cardiomyopathyo Ileus
• Contraindications:o Severe cardiac disorderso History of neutropenia / agranulocytosis
• Interactions:o Avoid concomitant use with drugs that have a high risk of
causing agranulocytosis (e.g. carbimazole)
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