Biological therapies for schizophrenia - Drug therapy Flashcards
What are antipsychotics?
Drugs used to reduce the intensity of symptoms, in particular the positive symptoms, of psychotic conditions like schizophrenia.
What is a typical antipsychotic?
The first generation of antipsychotic drugs, having been used since 1950s. Work as dopamine antagonists and include chlorpromazine.
What are the two types of antipsychotics used for schizophrenia?
Atypical and typical.
describe the function of chlorpromazine.
Can be taken as tablets, syrup or by injection. administered daily up to a max of 1000mg.
There is a strong association between the use of typical antipsychotics and the dopamine hypothesis.
Typical antipsychotics like chlorpromazine work by acting as antagonist in the dopamine system antagonists are chemicals which reduce the action of a neurotransmitter.
Dopamine antagonists work by blocking dopamine receptors in the synapses of the brain, reducing the action of dopamine. This normalises neurotransmission in key areas of the brain, reducing symptoms like hallucinations.
Chlorpromazine is also an effective sedative. It is often used to calm patients.
What is an atypical antipsychotic?
Drugs for schizophrenia developed after typical antipsychotics. They typically target a range of neurotransmitters such as dopamine and serotonin. Examples include clozapine and risperidone.
Been used since the 1970s, the aim was to maintain or improve upon the effectiveness of drugs in suppressing the symptoms of psychosis and also minimise the side effects.
Describe clozapine.
More effective than typical antipsychotics to be used when other treatments failed.
It has potentially fatal side effects So cannot be taken as an injection. people taking it have regular blood tests to ensure they are not developing agranulocytosis.
Daily dosage is lower than for chlorpromazine, typically 300-450mg a day.
Binds to dopamine receptors in the same way that chlorpromazine does, but also acts on serotonin and glutamate receptors.
Believed that this action helps improve mood and reduce depression and anxiety in patients, and that it may improve cognitive functioning - therefore t is sometimes prescribed when a patient is considered at high risk of suicide.
describe risperidone.
A more recently developed atypical antipsychotic, having been aroused since the 1990s. Developed in an attempt to produce a drug as effective as clozapine but without its serious side effects.
can be taken in the form of tablets, syrup or an injection that lasts for around two weeks. Dosage is a maximum of 12mg.
It is believed to bind to dopamine and serotonin receptors. Risperidone binds more strongly to dopamine receptors than clozapine and is therefore effective in much smaller doses than most antipsychotics.
there is some evidence to suggest that this leads to fewer side effects than is typical for antipsychotics.
Discuss evidence for effectiveness as a strength of drug therapy.
There is a large body of evidence to support the idea that both typical and atypical antipsychotics are at least moderately effective in tackling the symptoms of schizophrenia.
Thornley et al (2003) Reviewed studies comparing the effects of chlorpromazine to control conditions in which patients received a placebo so that experiences were identical except for the presence of the drug and their medication.
Data from 13 trials with a total of 1121 participants showed that the drug was associated with better overall functioning and reduced symptoms severity.
Data from three trials with a total of 512 participants showed that relapse rate was also lower when the drug was taken.
This suggests that antipsychotics are an effective treatment for the symptoms of schizophrenia increasing the value of the therapy.
ADDITIONALLY -
There is support for the benefits of atypical antipsychotics.
In a review researchers concluded that clozapine is more effective than typical antipsychotics and other atypical antipsychotics, and that it is effective in 30-50% of treatment resistant cases where typical antipsychotics have failed.
It does therefore seem that antipsychotics in general are reasonably effective, and this is a strength of drug therapy.
Discuss serious side effects as a limitation of drug therapy.
A problem with antipsychotic drugs is the likelihood of side effects, ranging from the mild to serious and even fatal.
Typical anti psychotics are associated with a range of side effects including dizziness, agitation, weight gain and itchy skin.
Long time use can result in tardive dyskinesia, which is caused by dopamine supersensitivity and manifests as involuntary facial movements such as grimacing, blinking and lip smacking.
A typical anti psychotics were developed to reduce the frequency of side effects and generally this has succeeded.
however, side effects still exist and patients taking clozapine have to have regular blood tests to alert doctors to early signs of agranulocytosis.
Side effects are thus still a significant weakness of antipsychotic drugs.
Discuss the use of the dopamine hypothesis was a limitation of drug therapies.
Our understanding of the mechanism of antipsychotic drugs is strongly associated with the dopamine hypothesis in its original form.
However, there is quite a bit of evidence to show that this original debut hypothesis is not a complete explanation for schizophrenia, and that in fact dopamine levels in parts of the brain other than the subcortex are too low rather than too high.
If this is true then it is not clear how antipsychotics, which are dopamine, can help with schizophrenia when they reduce dopamine activity.
A modern understanding of the relationship between dopamine and psychosis suggests that antipsychotics shouldn’t work.
This has undermined the faith of some people that antipsychotics do in fact work.
Discuss problems with the evidence for effectiveness as an imitation of drug therapies.
A limitation of drug therapy is that evidence for its effectiveness have been challenged.
Researchers have suggested that some successful trials have had their data published multiple times, exaggerating the evidence for positive effects.
Researchers also suggest that because antipsychotics have powerful calming effects, it is easy to demonstrate that they have some positive effect on patients. This is not the same as saying they’ve really reduced the severity of psychosis.
Additionally, most published studies assess short term benefits rather than long term benefits and compare patients who keep taking antipsychotics with those suffering withdrawal having just stopped taking them.
These issues suggest that antipsychotic drugs may not be that effective after all - greatly limiting our confidence in drug therapy.
It may also be that their effectiveness has been exaggerated by drug companies (who fund quite a lot of the research), and more independent research into drug therapy is therefore needed to assess their effectiveness in treating schz.
