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Schizophrenia: drugs

Schizophrenia: drugs. Synaptic transmission Mechanisms of drug action Drugs used with schizophrenia. psychlotron.org.uk. Neurones. Neuronal cell bodies. psychlotron.org.uk. Axons. Source: science photo library. Synapses occur at the junctions. Synapses.

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Schizophrenia: drugs

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  1. Schizophrenia: drugs • Synaptic transmission • Mechanisms of drug action • Drugs used with schizophrenia psychlotron.org.uk

  2. Neurones Neuronal cell bodies psychlotron.org.uk Axons Source: science photo library Synapses occur at the junctions

  3. Synapses • Neurones transmit signals electrically along their axons • The synapses (junctions between neurones) transmit signals chemically • Most drugs act by interfering with events at the synapse psychlotron.org.uk

  4. Synapse Vesicles filled with neurotransmitter psychlotron.org.uk Synaptic cleft Source: neuroscience.wustl.edu Location of receptors (post-synaptic density)

  5. psychlotron.org.uk Vesicles release neurotransmitter into synaptic cleft

  6. psychlotron.org.uk Neurotransmitter binds to receptors & activates them

  7. psychlotron.org.uk Enzymes are released to break down the neurotransmitter

  8. psychlotron.org.uk Excess neurotransmitter is taken up by the pre-synaptic neurone

  9. psychlotron.org.uk Vesicles are replenished with new & reused neurotransmitter

  10. Drug Therapies • Increase synaptic activity by: • Causing more neurotransmitter to be released • Introducing a chemical that acts like the neurotransmitter • Preventing breakdown of neurotransmitter • Preventing reuptake of neurotransmitter psychlotron.org.uk

  11. Drug therapies • Decrease activity by: • Increasing rate of neurotransmitter breakdown • Blocking off receptors psychlotron.org.uk

  12. Antipsychotic medication • Neuroleptics (e.g. chlorpromazine) bind to DA receptors without activating them psychlotron.org.uk

  13. psychlotron.org.uk

  14. psychlotron.org.uk

  15. Effectiveness • Older (typical) drugs (e.g. chlorpromazine) • Short term beneficial effect in 75% of patients (Davis et al, 1989) • Long term beneficial effect in 55-60% (Davis et al, 1993) • Most effective against positive symptoms • High risk of side effects psychlotron.org.uk

  16. Side effects • Extrapyramidal side effects (EPS) • Parkinson’s-type symptoms • Postural & motor abnormalities • Other side effects • Sedation • Weight gain • Seizures psychlotron.org.uk

  17. Effectiveness • Newer (atypical) drugs (e.g. clozapine) • As effective as typical drugs on positive symptoms; better for negative symptoms (Bilder et al, 2002) • More effective with treatment-resistant patients (DeNayer et al, 2003) • Less risk of EPS, but other side effects may occur (e.g. blood disorders) psychlotron.org.uk

  18. Typical vs. atypical tightly bound; slow release from receptor loosely bound; fast release from receptor psychlotron.org.uk Drug DA receptor

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