Tuesday, 9 November 2010

MRCP revision battle 44.1: Antipsychotic medication

Today is a psychiatry and overdose fest...

MRCP revision battle 44.1: Antipsychotic medication
MRCP revision battle 44.2: SSRIs
MRCP revision battle 44.3: Serotonin syndrome
MRCP revision battle 44.4: Baby blues, post natal depression and psychosis
MRCP revision battle 44.5: Quinine toxicity/overdose
MRCP revision battle 44.6: Theophylline overdose
MRCP revision battle 44.7: Ethylene glycol poisoning

MRCP revision battle 44.1: Antipsychotic medication

Antipsychotic medications are used in the treatment of schizophrenia, severe anxiety, mania and occasionally for their sedative properties.

Antipsychotic medications have an immediate sedative action but their antipsychotic action may tak up to 3 weeks to become effective.

Atypical antipsychotics

Atypical antipsychotics are the newer drugs.  They produce a highly selective blockade of the mesolimbic D2 receptors and serotonin 5HT2A receptors.

Examples include amisulperide, olanzapine, quetiapine, risperidone and clozapine.

Side effects include:
  • weight gain
  • nausea, dyspesoa
  • hyperglucaemia and impaired glucose tolerance
  • increased risk DVT
  • increased risk stroke (especially olanzapine and risperidone)
  • clozapine only:
    • 1% agranulocytosis/neutropenia - therefore weekly blood tests for 1st 6 months then fortnightly afterwards
    • 3% seizures

All antipsychotics have roughly the same effectiveness except clozapine, which is better.  However, in light of its worse side effect profile clozapine is only recommended if 2 others have already failed.

Typical antipsychotics

Typical antipsychotics are the older drugs,
Examples include haloperidol, chorpromazine, phenothiazine and sulperide.

Side effects of the typical antipsychotics include:
  • extrapyramidal side effects
  • anticholingergic effects
  • antihistaminergic effects
  • photosensitivity (especially phenothiazine)
  • prolonged QT
  • lower seizure threshold
  • hyperprolactinaemia.

Now on to SSRIs...