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Risperidone

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Risperidone chemical structure
Risperidone

4-[2-[4-(6-fluorobenzo[d]isoxazol-3-yl)-
1-piperidyl]ethyl]-3-methyl-
2,6-diazabicyclo[4.4.0]deca-1,3-dien-5-one
IUPAC name
CAS number
106266-06-2
ATC code

N05AX08

PubChem
5073
DrugBank
APRD00187
Chemical formula {{{chemical_formula}}}
Molecular weight 410.485 g/mol
Bioavailability 70% (oral)
Metabolism Hepatic (CYP2D6-mediated)
Elimination half-life 3–20 hours
Excretion Urinary
Pregnancy category C
Legal status Rx-only
Routes of administration Oral and extended-release intramuscular injection



Risperidone (pronounced Ris-PER-ǐ-dōn and sold under the trade name Risperdal in the Netherlands, United States, Canada, the United Kingdom, [Portugal and several other countries, Risperdal or Ridal in New Zealand, Rispolept in Eastern Europe, and Belivon, or Rispen elsewhere) is an atypical antipsychotic developed by Janssen-Cilag.

UsesEdit

Risperidone was approved by the United States Food and Drug Administration (FDA) in 1993[1] for the treatment of schizophrenia. On August 22, 2007, Risperdal was approved as the only drug agent available for treatment of schizophrenia in youth ages 13–18; it was also approved that same day for treatment of bipolar disorder in youth and children ages 10–18, joining lithium. Risperidone contains the functional groups of benzisoxazole and piperidine as part of its molecular structure. In 2003 the FDA approved risperidone for the short-term treatment of the mixed and manic states associated with bipolar disorder. In 2006 the FDA approved risperidone for the treatment of irritability in children and adolescents with autism. The FDA's decision was based in part on a study of autistic children with severe and enduring problems of tantrums, aggression, and self-injury; risperidone is not recommended for autistic children with mild aggression and explosive behavior without an enduring pattern.[2] Like other atypical antipsychotics, risperidone has also been used off-label for the treatment of anxiety disorders, such as obsessive-compulsive disorder; severe, treatment-resistant depression with or without psychotic features; Tourette syndrome; disruptive behavior disorders in children; and eating disorders, among others.[3] In two small studies risperidone was reported to successfully treat the symptoms of phencyclidine psychosis due to acute intoxication[4] and chronic use.[5]

A multi-year UK study by the Alzheimer's Research Trust suggested that this and other neuroleptic anti-psychotic drugs commonly given to Alzheimer's patients with mild behavioural problems often made their condition worse. The study concluded that:

For most patients with AD, withdrawal of neuroleptics had no overall detrimental effect on functional and cognitive status and by some measures improved functional and cognitive status. Neuroleptics may have some value in the maintenance treatment of more severe neuropsychiatric symptoms, but this possibility must be weighed against the unwanted effects of therapy.[6]

Patent statusEdit

Janssen's patent on Risperdal expired on December 29, 2007, opening the market for cheaper generic versions of the drug from other companies; however, Janssen had exclusive marketing rights until June 29, 2008, as the result of a pediatric extension.

Risperidone is available as a tablet in 0.25, 0.5, 1, 2, 3 and 4 mg sizes, as an oral solution (30ml, 1mg/ml), and as a 25 mg, 37.5 mg and 50 mg ampoule Risperdal Consta, which is a depot injection administered once every two weeks. It is also available as a wafer known in the United States as Risperdal M-Tabs and elsewhere as Risperdal Quicklets.

Generic AvailabilityEdit

Risperdone became available as a generic drug in October 2008 from Teva Pharmaceuticals and Patriot Pharmaceutics. The Patriot generic is Janssen Pharmaceutical's "authorized generic pharmaceutical."

File:Risperdal tablets.jpg

Side effectsEdit

Common side effects include akathisia, anxiety, insomnia, low blood pressure, muscle stiffness, muscle pain, sedation, sexual dysfunction, tremors, increased salivation, and stuffy nose. Risperidone has been associated with minimal to moderate weight gain, with one study finding that 26 to 38 percent of participants on the drug experienced weight gain.[7][8]

Occasionally breast tenderness and eventually lactation in both genders may occur. Many antipsychotics are known to increase prolactin because they inhibit dopamine. However, risperidone is known to increase prolactin to a greater extent than most other antipsychotics, such as quetiapine. It is thought that once risperidone raises prolactin, it may cause non-cancerous tumors in the pituitary gland. This may recur even if the patient has switched to a different antipsychotic.[9]

Risperidone can potentially cause tardive dyskinesia (TD),[10] extrapyramidal symptoms (EPS),[10] and neuroleptic malignant syndrome (NMS).[10]

Also, Risperidone can trigger diabetes and more serious conditions of glucose metabolism, including ketoacidosis and hyperosmolar coma.[11]

PharmacologyEdit

This drug belongs to a class of anti-psychotic drugs known as atypical neuroleptics. It is a strong dopamine antagonist. It has high affinity for D2 dopaminergic receptors. It has actions at several 5-HT (serotonin) receptor subtypes. These are 5-HT2C, linked to weight gain, 5-HT2A,linked to its antipsychotic action and relief of some of the extrapyramidal side effects experienced with the typical neuroleptics through action at 5-HT1A. The latter action may lead to an increased release of dopamine from mesocortical neurones in the brain.

It reaches peak plasma levels quickly regardless of whether it is administered as a liquid or pill. Risperidone is metabolised fairly quickly, so this potential for nausea subsides usually in two to three hours. However, the active metabolite, 9-hydroxy-risperidone, which has similar pharmacodynamics to risperidone, lingers in the body for much longer, and has been developed as an antipsychotic in its own right, called paliperidone.

An intramuscular preparation, marketed as Risperdal Consta, can be given once every two weeks. It is slowly released from the injection site. It can be useful in patients who have difficulty taking oral medication for any reason. Some people prefer a once-every-two-weeks injection to daily pills[How to reference and link to summary or text]. It also helps the physician ensure compliance. Doses range from 25 to 50 mg given as an intramuscular injection once every two weeks.

ReferencesEdit

  1. (2007). Electronic Orange Book. Food and Drug Administration. URL accessed on 2007-05-24.
  2. Scahill L (2008). How do I decide whether or not to use medication for my child with autism? should I try behavior therapy first?. J Autism Dev Disord 38 (6): 1197–8.
  3. FDA (October 2, 2006). FDA Approves the First Drug to Treat Irritability Associated with Autism, Risperdal. Press release. Retrieved on 2006-10-02.
  4. AJ Giannini, GL Colapietro, DK Cook. Risperidone therapy in phencyclidine intoxication, Society for Neuroscience Abstracts. 22:77.12, 1996.
  5. JF Gabbert,AJ Giannini. Dopaminergic/serotonergic actions of phencyclidine as a model for schizophrenia psychosis. American Journal of Therapeutics. 4:159-164, 1997.
  6. Ballard C, Lana MM, Theodoulou M et al. (2008). A randomised, blinded, placebo-controlled trial in dementia patients continuing or stopping neuroleptics (the DART-AD trial). PLOS Medicine 5 (4): e76.
  7. Vanina et al. (July 2002). Body Weight Changes Associated With Psychopharmacology. Psychiatric Services 53: 842–847.
  8. Baldwin, D and Mayers, A. (2003). Sexual side-effects of antidepressant and antipsychotic drugs. Advances in Psychiatric Treatment 9: 202–210.
  9. Szarfman A, Tonning J, Levine J, Doraiswamy P (2006). Atypical antipsychotics and pituitary tumors: a pharmacovigilance study.. Pharmacotherapy 26 (6): 748–58.
  10. 10.0 10.1 10.2 Risperdal: Full U.S. Prescribing Information. (PDF) publisher=Ortho-McNeil-Janssen Pharmaceuticals. URL accessed on 2008-03-06.
  11. FDA (April 19, 2004). FDA Warning Letter. Press release. Retrieved on 2007-05-02.

External linksEdit

Template:Dopamine antagonists Template:Serotonin antagonists

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