biological therapy for schizophrenia Flashcards
drug therapy
- antipsychotic drugs
- psychosis is defining characteristic of schizophrenia
- may be required in long or short term
- some people take short course and then stop use without return of symptoms
- others may require antipsychotics for life
- divided into typical and newer atypical drugs
typical antipsychotics
- been around since 1950s
- typical prescribed doses have declined over the last 50 years
dopamine antagonists -
- strong association between use of typical antipsychotics and dopamine hypothesis
- typical antipsychotics works by acting as antagonists in dopamine system
- antagonists reduce action of a neurotransmitter
- dopamine antagonists block dopamine receptors in synapses of brain, reducing action of dopamine
- according to dopamine hypothesis, this dopamine-antagonist effect normalises neurotransmission in key areas of the brain, reducing symptoms such as hallucinations
sedation effect -
- antipsychotics such as chlorpromazine are effective sedatives
- believed to be related to effect on histamine receptors, not fully understood how this leads to sedation
- chlorpromazine often used to calm individuals with all sorts of conditions
- often done when patients are first admitted to hospital and they feel anxious
- syrup absorbed faster than tablets, tends to be used when chlorpromazine is given for sedative properties
atypical antipsychotics
- used since 1970s
- aim was to maintain or improve effectiveness in suppressing symptoms of psychosis and also minimise side effects of drugs
- not all atypical antipsychotics work in same way
clozapine -
- discovered to be more effective than typical antipsychotics in 1980s, to be used when other treatments failed
- people taking it have regular blood tests to ensure they are not developing agranulocytosis
- not available as an injection due to potentially fatal side effects
- daily dosage is lower than that for chlorpromazine
- clozapine binds to dopamine receptors in same way as chlorpromazine, also acts on serotonin and glutamate receptors
- this action helps to improve mood and reduce depression and anxiety, may improve cognitive functioning
- mood enhancing effects mean it is sometimes prescribed when an individual is at high risk of suicide
- 30-50% of people with schizophrenia attempt suicide at some point
risperidone -
- developed in attempt to produce drug as effective as clozapine but without serious side effects
- can be taken in form of tablets, syrup or an injection
- believed to bind to dopamine and serotonin receptors
- binds more strongly to dopamine receptors than clozapine, effective in much smaller doses
- some evidence to suggest this leads to fewer side effects than other antipsychotics
evaluation strength - evidence for effectiveness
- Thornley reviewed studies comparing effects of chlorpromazine to control conditions
- data from 13 trials showed that chlorpromazine was associated with better overall functioning and reduce symptom severity, compared to placebo
- Meltzer concluded that clozapine is more effective than typical antipsychotics and other atypical antipsychotics, effective in 30-50% of treatment-resistant cases
evaluation limitation - counterpoint to evidence for effectiveness
- Healy suggested serious flaws with evidence
- most studies are of short-term effects only
- some successful trials have had data published multiple times, exaggerating the size of their evidence base
- because antipsychotics have calming effects, it is easy to demonstrate that they have some positive effect on those with schizophrenia symptoms
- not the same as saying they really reduce the severity of psychosis
- evidence bases for effectiveness of antipsychotics is less impressive than it first appears
evaluation limitation - serious side effects
- typical antipsychotics associated with side effects like dizziness, agitation, weight gain and itchy skin
- long-term use can result in tardive dyskinesia, caused by dopamine supersensitivity, causes involuntary facial movements such as grimacing
- most serious side effect is neuroleptic malignant syndrome (NMS)
- caused when drug blocks dopamine action in the hypothalamus
- NMS results in high temperature, delirium etc. and can be fatal
- antipsychotics do harm as we as good, individuals who experience side effects may avoid such treatments, making them ineffective
evaluation limitation - mechanism unclear
- understanding of mechanism by which antipsychotic drugs work is tied up with original dopamine hypothesis (idea that symptoms are linked to high levels of dopamine activity in sub cortex of brain)
- we know that original dopamine hypothesis is not a complete explanation, and that dopamine levels in other parts of the brain are too low rather than high
- if this is true, most antipsychotics should not work
- this adds to the argument that they are ineffective
- some antipsychotics may not be best treatment, as perhaps some other factor is involved in their apparent success
how antipsychotic drugs work on the dopaminergic system
- typical and atypical drugs work in the same way on dopamine systems
- inhibit DA transmitters from binding onto the receptor site on the post-synaptic neuron
- usually there is an initial increase in DA levels whilst the system adapts but this leads to lower levels over time
- leads to reduced symptoms, mostly positive ones
- link to synaptic transmission
