Antipsychotics

Indications

  • schizophrenia
    • good for relieving 'positive' symptoms
    • clozapine and risperidone may be better against 'negative' symptoms
  • mania
  • Tourette's syndrome
  • agitation
Group Oral Depot
Phenothiazines
  • chlorpromazine
  • thioridazine
  • trifluoperazine
  • fluphenazine
butyrophenones
  • haloperidol
  • droperidol
  • haloperidol
thioxanthines
  • flupenthixol
  • clopehtixol
  • flupenthixol
  • clopenthixol
diphenylbutylpiperidines
  • pimoxide
  
benzamides
  • sulpiride
  • amisulpride
  
atypical
  • clozapine
  • risperidone
  • quetiapine
  • zotepine
  • olanzapine
  

Atypical

  • generally weaker D2 Antagonists
  • Often D1/D4 receptor antagonists
  •  may also have weaker action on 5-HT2, Musc ACh, a1-Adrenoceptors, H1.receptors 
  • hence
    • REDUCED Extrapramidal motor syndromes
    • REDUCED General side effects
    • REDUCED negative symptoms
    • INCREASED Social rehabilitation possibly due to less cognitive impairment

These are becoming 1st line drugs despite cost differences

Mechanism of action

  • block dopamine receptors
    • nigro striatal
    • meso limbic/cortical
    • tubero hypophyseal
  • also block cholinergic, adrenergic and histaminic receptors
  • phenothiazines and butyrophenones relatively non-selective
  • benzamides highly selective D2 blockers
  • Atypicals block 5HT2 receptors as well

Pharmacokinetics

  • Lipid soluble- high vol of distribution 90% bound to protein 
  • Almost all metabolised in liver none excreted in urine

Side-effects

Variations

  • Olanzapine
    • reduced risk of agranulocytosis
  • Risperidone
    • few side effects

Alleviating Side Effects

  • Acute dystonia, parkinsonism respond to anticholinergics e.g. procyclidine
  • ? betablockers or benzodiazepines may be helpful
  • tetrabenazine may reduce tardive dyskinesia
 

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