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Oxford Assess and Progress: Psychiatry$
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Gil Myers, Melissa Gardner, Katharine Boursicot, and David Sales

Print publication date: 2014

Print ISBN-13: 9780199665662

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780199665662.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 26 November 2021



(p.169) Chapter 6 Psychopharmacology
Oxford Assess and Progress: Psychiatry

Kazuya Iwata

Oxford University Press

Psychotropic drugs are the main form of physical treatment in psychiatry and they exert their action by mainly acting on dopamine, noradrenaline, serotonin, and muscarinic receptors. Antipsychotics, which are the mainline treatment for psychotic ill–nesses, usually act by blocking dopamine receptors in the dopamine pathways of the brain, usually the mesolimbic system. The D2 receptors are the usual target of the antipsychotics, although clozapine, which is considered the gold standard antipsychotic, has a strong affinity for the D4 receptors. The underlying principle of antipsychotic treatment builds on the dopamine theory of schizophrenia, whereby an excess of dopa–mine is linked to the development of psychotic symptoms. Overactive dopamine receptors are thought to be involved in this, and thus block–age of the dopamine receptors through antipsychotics can provide relief from psychotic symptoms. Antipsychotics are divided into typical and atypical, and the defining feature of typicals is their propensity to cause EPSEs. This is thought to be due to the fact that typical antipsychotics are not specific for dopa–mine receptors in the mesolimbic pathways, but can also block those in mesocortical, tuberoinfundibular, and nigrostriatal pathways. Atypical antipsychotics can impact on a variety of receptor types, such as serotonin, and thus they are usually subclassified according to their pharmacological properties. Their heterogeneous pharmacodynamics in part explains their variable side-effect profile. One common side-effect of atypical antipsychotics is their tendency to trigger metabolic syndrome, which is a cluster of cardiovascular risk factors including dyslipidaemia, hypertension, central obesity, and impaired glucose tolerance. They also cause endocrine-related side-effects, such as hyperprolactinaemia. An important adverse effect seen with any antipsychotic is neuroleptic malignant syndrome (NMS), which is an idiosyncratic reaction to antipsy–chotics taken even at therapeutic doses. Patients can present with hyper–thermia, rigidity, autonomic disturbances, and altered mental state over 24–48 hours. It can be potentially life threatening, and thus, if suspected, urgent referral to a general hospital is required. Antidepressants also vary greatly with regards to their pharmacologi–cal properties, but the majority increase the concentration of neuro–transmitters in the synaptic cleft to alleviate depressive symptoms.

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