Properties of the neuroleptic class of drugs
Schizophrenia is associated with increased activity in the dopaminergic system. Many antipsychotic drugs (neuroleptics) exert their therapeutic effects by D2 receptor blockade. There are 2 main categories of neuroleptics – typical (eg chlorpromazine, haloperidol) and atypical (eg clozapine, risperidone). The difference between the two types include fewer extrapyramidal side effects with atypical antipsychotics, and greater efficacy in treatment-resistant patients and against negative symptoms also with atypical antipsychotics. The neuroleptics show varying patterns of selectivity at receptor sites. Older neuroleptics such as chlorpromazine show greater affinity for D2 receptors compared with D1 receptors. Some of the newer agents (eg sulpiride) are highly selective for D2 receptors, whereas clozapine is relatively non-selective for D1 or D2, but has high affinity for D4. Important side effects common to most neuroleptics are extrapyramidal motor disturbances and endocrine disturbances (increased prolactin secretion), which are secondary to dopamine receptor antagonism. Other side effects (eg dry mouth, blurred vision, sedation, hypotension, etc.) are due to blockade of receptors such as α-adrenoceptors, muscarinic cholinergic receptors and histamine H1 receptors. Additionally, rare idiosyncratic reactions can occur; obstructive jaundice has been reported with chlorpromazine therapy, leukopenia can occur with clozapine and thioridazine has been associated with cardiac conduction defects.
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References
Antipsychotic drugs. In: Pharmacology, 4th edition. Rang HP, Dale MM and Ritter JM. Edinburgh, UK: Harcourt Publishers Ltd, 2001:539–549.
Schizophrenia. National Electronic Library for Mental Health.