drug therapy Flashcards
What is the difference between atypical antipsychotics and typical antipsychotics
Typical Antipsychotics – Traditional antipsychotics which have been around since the 1950s used to treat positive symptoms, e.g. Chlorpromazine.
Atypical Antipsychotics – Newer antipsychotics which have been used since the 1970s combat positive symptoms but also claim to have an impact on negative symptoms and cognitive impairment as well, e.g. Clozapine and Risperidone.
How do typical antipsychotics work
There is a strong association between the use of typical antipsychotics and the dopamine hypothesis. Typical antipsychotics works as antagonists 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. According to the dopamine hypothesis of schizophrenia, this dopamine-antagonist effect normalises neurotransmission in key areas of the brain, reducing symptoms like hallucinations and delusions.
Hallucinations and delusions usually diminish within a few days of beginning medication, although other symptoms may take several weeks before a significant improvement is seen. Chlorpromazine is also an effective sedative which can be useful when patients first enter psychiatric hospitals and are very anxious.
However, other receptors in the brain are also blocked when using typical antipsychotics which leads to undesirable side effects. This problem has been addressed by developing atypical antipsychotics.
How do atypical antipsychotics work
As with typical antipsychotics these drugs also act on the dopamine system by blocking dopamine receptors. However, they only temporarily occupy the dopamine receptors and then rapidly separate to allow normal dopamine transmission. This is thought to cause lower levels of side effects compared to typical antipsychotics and also makes them suitable for treatment-resistant patients.
Atypical antipsychotics also bind to serotonin receptors as well as dopamine receptors which help to improve mood and reduce depression and anxiety in patients, which in turn improves cognitive functioning.
Evaluation
P - One limitation of antipsychotic drugs is the likelihood of side effects.
E - Typical antipsychotics are associated with a range of side effects including dizziness, agitation, sleepiness, stiff jaw, weight gain and itchy skin. Long-term use can result in tar dive dyskinesia - caused by dopamine super sensitivity and causes involuntary facial movements such as grimacing, blinking and lip-smacking. Arguably the most serious side effect of antipsychotics (particularly typical) is neuroleptic malignant syndrome (NMS). This is caused when the drug blocks dopamine action in the hypothalamus. NMS results in a high temperature, delirium and coma, and can be fatal.
E - Therefore, antipsychotics can do harm as well as good and individuals who experience these may avoid such treatments due to these side-effects as they prevent patients from carrying on their everyday lives (for example in work) which could lead to high attrition rates and therefore negative impacts on the economy, thus making the treatment ineffective.
P - One strength of antipsychotics is that there is empirical evidence to support for their effectiveness.
E - Thornley et al. (2003) reviewed studies comparing the effects of chlorpromazine to control conditions. Data from 13 trials with a total of 1121 participants showed that chlorpromazine was associated with better overall functioning and reduced symptom severity as compared to placebo.
E - This is a strength as there is evidence to suggest that antipsychotics work.
Counterpoint: However Healy (2012) suggested that there are serious flaws with evidence for effectiveness. Most studies are of short-term effects only and some exaggerate the size of the evidence base for positive effects which lowers the reliability of the evidence. Since antipsychotics have powerful calming effects there is a difference in explaining the reduced severity of psychosis compared to the positive effects on people experiencing symptoms of schizophrenia. This is contradicting the evidence base for antipsychotic effectiveness as it seems to be less impressive that it first appears.
P - There is evidence to suggest that there are advantages of atypical over typical antipsychotics.
E - Crossley et al (2010) carried out a meta-analysis of 15 studies to examine the efficacy and side effects of atypical and typical antipsychotics. It was found that people on typical antipsychotics experienced more extrapyramidal side effects. In addition, atypical antipsychotics help to reduce negative symptoms such as avolition and because they also act on serotonin receptors, they can reduce anxiety and depression. This makes it more likely that patients will continue with their medication, because it will increase their motivation to take it, due to the reduction of the negative consequences.
E - This means that they are more likely to see a reduction in their symptoms meaning they can cope better with everyday life. As a result they may be able to enter the workforce and contribute to the economy suggesting that atypical antipsychotics also have positive implications for the economy.
