Blockade of dopaminergic D_ receptors in the limbic system alleviates positive symptoms of schizophrenia such as hallucinations, delusions, and erratic behavior and speech. Blockade of serotonergic 5-HT_ receptors in the mesocortical tract, causes an excess of dopamine and an increase in dopamine transmission, resulting in an increase in dopamine transmission and an elimination of core negative symptoms. Dopamine receptors in the nigrostriatal pathway are not affected by risperidone and extrapyramidal effects are avoided. Like other 5-HT_ antagonists, risperidone also binds at alpha(1)-adrenergic receptors and, to a lesser extent, at histamine H1 and alpha(_)-adrenergic receptors.

Risperidone is an atypical antipsychotic medication. It is most often used to treat delusional psychosis (including schizophrenia), but risperidone is also used to treat some forms of bipolar disorder and psychotic depression. It also has shown some success in treating symptoms of Asperger's Syndrome and autism. Risperidone is now the most commonly prescribed antipsychotic medication in the United States.

Extensively metabolized by hepatic cytochrome P450 2D6 isozyme to 9-hydroxyrisperidone, which has approximately the same receptor binding affinity as risperidone. Hydroxylation is dependent on debrisoquine 4-hydroxylase and metabolism is sensitive to genetic polymorphisms in debrisoquine 4-hydroxylase. Risperidone also undergoes N-dealkylation to a lesser extent.

Symptoms of overdose include drowsiness, sedation, tachycardia, hypotension, and extrapyramidal symptoms. LD₅₀=82.1mg/kg (orally in mice).

1. Altschuler EL, Kast RE: The atypical antipsychotic agents ziprasidone [correction of zisprasidone], risperdone and olanzapine as treatment for and prophylaxis against progressive multifocal leukoencephalopathy. Med Hypotheses. 2005;65(3):585-6. Pubmed
2. Bostwick JR, Guthrie SK, Ellingrod VL: Antipsychotic-induced hyperprolactinemia. Pharmacotherapy. 2009 Jan;29(1):64-73. Pubmed
3. Fenton C, Scott LJ: Risperidone: a review of its use in the treatment of bipolar mania. CNS Drugs. 2005;19(5):429-44. Pubmed
4. Kemp DE, Canan F, Goldstein BI, McIntyre RS: Long-acting risperidone: a review of its role in the treatment of bipolar disorder. Adv Ther. 2009 Jun;26(6):588-99. Epub 2009 Jun 26. Pubmed
5. Szarfman A, Tonning JM, Levine JG, Doraiswamy PM: Atypical antipsychotics and pituitary tumors: a pharmacovigilance study. Pharmacotherapy. 2006 Jun;26(6):748-58. Pubmed
6. Urichuk L, Prior TI, Dursun S, Baker G: Metabolism of atypical antipsychotics: involvement of cytochrome p450 enzymes and relevance for drug-drug interactions. Curr Drug Metab. 2008 Jun;9(5):410-8. Pubmed
7. Yamanouchi Y, Iwata N, Suzuki T, Kitajima T, Ikeda M, Ozaki N: Effect of DRD2, 5-HT2A, and COMT genes on antipsychotic response to risperidone. Pharmacogenomics J. 2003;3(6):356-61. Pubmed