typical antipsychotic drugs (e.g. chlopromazine) have been around since the 1950s.
they aim to work by acting as antagonists in the dopaminesystem and aim to reduce the action of dopamine - they are stronglyassociated with the dopamine hypothesis
Typical antipsychotics: block dopamine receptors in synapses
dopamine antagonists work by blockingdopamine receptors in synapses in the brain, reducing the action of dopamine
initially, dopamine levels build up after taking chlopromazine, but then production is reduced
this normalizesneurotransmission in key areas of the brain, which turn reducessymptoms like hallucinations
Typical antipsychotics: Chorpromazine side effect
chlorpromazine also has an effect on histaminereceptors which appears to lead to a sedation effect
it is also used generally to calmanxiouspatients when they are firstadmitted to the hospital
Typical antipsychotics: chlorpromazine
taken in form of tablets, syrup or injection
dosage: max of 1000mg a day but typically 400-800mg
Atypical antipsychotics:
the aim of developing newerantipsychotics was to maintain or improve upon the effectiveness of drugs in suppressing the symptoms of psychosis and also to minimizeside effects of the drugs used
Atypical antipsychotics: clozapine
clozapine binds to dopamine receptors as chlorpromazine does, but it also acts on serotonin and glutamatereceptors
this drug was more effective than typicalantipsychotics - clozapine reducesdepression and anxiety as well as improving cognitivefunctioning
it also improves mood, which is important as up to 50% of people with sz attemptsuicide
Atypical antipsychotics: risperidone
risperidone was developed in the 1990s because clozapine was involved in the deaths of some people from a bloodcondition called agranulocytosis
risperidone, like clozapine binds to dopamine and serotoninreceptors
but risperidone binds more strongly to dopaminereceptors and is therefore more effective in smaller doses than most antipsychotics and has fewerside effects
One strength of antipsychotics is evidence of their effectiveness.Thornley et al. (2003) reviewed data from 13 trials (1121 ppts) and found that chlopromazine was associated with betterfunctioning and reducedsymptomseverity compared with a placebo. There is also support for the benefits of atypical antipsychotics. Meltzer (2012) concluded that clozapine is more effective than typical antipsychotics, and that it is effective in 30-50% of treatment-resistantcases. This means that as far as we can tell, antipsychoticswork.
Counterpoint for evidence of antipsychotics effectiveness
However, most studies are of short-termeffects only and some datasets have been publishedseveral times, exaggerating the size of the evidencebase (Healy 2012). Also benefits may be due to calming effects of drugs rather than real effects on symptoms. This means evidence of effectiveness is lessimpressive than it seems.
One limitation of antipsychotic drugs is the likelihood of side effects.Typical antipsychotics are associated with dizziness, agitation, sleepiness, weight gain, etc. Long-term use can lead to lip-smacking and grimacing due to dopaminesuper-sensitivity (= tardive dyskenesia). The most serious side effect is neurolepticmalignantsyndrome (NMS) caused by blocking dopamine action in the hypothalamus (can be fatal due to disruptedregulation of severalbody systems). This means that antipsychotics can do harm as well as good and individuals may avoid them (reducing effectiveness)
Another limitation of antipsychotics is that we do not know why they work. The use of most of these drugs is stronglytied up with the dopamine hypothesis and the idea that there are higher-than-usual levels of dopamine in the subcortex of people with sz. But there is evidence that this may not be correct and that dopamine levels in other parts of the brain are too low rather than too high. If so, most antipsychotics shouldn'twork. This means that antipsychotics may not be the besttreatment to opt for - perhaps some other factor is involved in their apparentsuccess.
Furthermore, it is believed that antipsychotics are used in hospitalsituations to calm people with sz and make them easier for staff to work with. However, calming people distressed by hallucinations and delusions probably makes them feelbetter and allows them to engage with other treatments (e.g. CBT) and services. On balance then there are clear benefits to using antipsychotics to calm people with sz and in the absence of a betteralternative they should probably be prescribed.
Atypical antipsychotics:
Clozapine
not available as an injection because of side effects, but taken in tablets and liquid.
dosage: typically 300-450mg a day
Risperidone
taken in form of syrup, tablets, or injections which last about 2 weeks
dosage: typically 4-8mg a day or max of 12mg a day