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 illnesses, 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 dopamine is linked to the development of psychotic symptoms. Overactive dopamine receptors are thought to be involved in this, and thus blockage 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 dopamine 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 antipsychotics taken even at therapeutic doses. Patients can present with hyperthermia, 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 pharmacological properties, but the majority increase the concentration of neurotransmitters in the synaptic cleft to alleviate depressive symptoms.
Prescribing patterns for psychotic and behavioural symptoms in dementia: a national survey
