Biological therapies for Schizophrenia: Drug Therapy Flashcards
What are antipsychotics?
Drugs used to reduce the intensity of symptoms, in articular the positive symptoms, of psychotic conditions like schizophrenia.
What are typical antipsychotics?
The first generation of antipsychotic drugs, having been used since the 1950s. They work as dopamine antagonists and include Chlorpromazine.
What are antagonists?
Chemicals which reduce the action of a neurotransmitter.
What are dopamine antagonists?
Dopamine antagonists work by blocking dopamine receptors in the synapses of the brain, reducing the action of dopamine.
How does Chlorpromazine treat symptoms of schizophrenia?
When they begin taking Chlorpromazine dopamine levels build up, but then its production is reduced. According to the dopamine hypothesis this dopamine-antagonist effect normalises neurotransmission in areas of the brain, reducing symptoms like hallucination.
What are atypical antipsychotics?
Drugs for schizophrenia developed after typical antipsychotics. They typically target a range of neurotransmitters such as dopamine and serotonin. E.g. Clozapine and Risperidone
What is Clozapine?
Clozapine was found to cause a blood condition called agranulocytosis.
Found to be more effective than typical antipsychotics, so remarketed as a backup treatment.
How do they now protect Clozapine users against agranulocytosis?
People have to take regular blood tests to ensure they are not developing agranulocytosis.
How does Clozapine work in schizophrenia patients?
Clozapine binds to dopamine receptors in the same way Chlorpromazine does, but it also acts on serotonin and glutamine receptors. This action improves mood and reduces anxiety and depression in patients, and this improves cognitive functioning.
What is Risperidone?
It was developed in an attempt to find a drug as effective as Clozapine without the side effects.
How does Risperidone work?
It binds to the dopamine and serotonin receptors. It binds more strongly to the dopamine receptors than Clozapine and is therefore effective in much smaller doses than most antipsychotics. This lead to fewer side effects.
What is the evaluation for drug therapy of schizophrenia?
Evidence for effectiveness
Serious side effects
Antipsychotics depend on the dopamine hypothesis
The chemical cosh argument
Evaluation point for drug therapy of schizophrenia: Evidence for effectiveness
Thornley reviewed studies comparing the effects of Chlorpromazine to control conditions in which patients received a placebo. Data from 13 trials with a total of 1121 participants showed that Chlorpromazine was associated with better overall functioning and reduced symptom severity.
Herbert Meltzer also found that Clozapine is effective in 30-50% of treatment-resistant cases.
There is clear evidence that anti-psychotics in general are reasonably effective, which is a strength.
Evaluation point for drug therapy of schizophrenia: Serious side effects
Typical anti-psychotics side effects = dizziness, agitation, sleepiness, stiff jaw, weight gain and itchy skin.
Long-term use can result in tardive dyskinesia.
The worst side effects is NMS, this is believed to be caused because the drug blocks dopamine action in the hypothalamus. Frequency 0.1% to just over 2%.
Atypical antipsychotics were introduced to reduce side effects and this has generally succeeded. Side effects are a significant weakness of antipsychotics drugs.
Evaluation point for drug therapy of schizophrenia: Antipsychotics depend on the dopamine hypothesis
There is evidence to show that the dopamine hypothesis is not a complete explanation for schizophrenia, and that inn fact dopamine levels are too low rather than too high. If this is true then it is not clear how antipsychotics, which are dopamine antagonists, can help with schizophrenia when they reduce dopamine activity.
This has undermined the faith of some people that antipsychotics do in fact work.
