title: Predominant role of the 9-hydroxy metabolite of risperidone in elevating blood prolactin levels.
abstract: OBJECTIVE
  The atypical antipsychotic risperidone significantly raises plasma prolactin levels in patients, but clozapine, olanzapine, and quetiapine do not. The differences in neuroendocrine response may be connected with the metabolism of the medications. The authors examined the contributory role of risperidone's active metabolite 9-hydroxy-risperidone by measuring plasma concentrations of risperidone, 9-hydroxy-risperidone, and prolactin.
  
  
  METHODS
  Blood samples taken from 25 patients with psychotic disorders following 6 weeks of treatment with risperidone (mean dose=3 mg/day) were examined. Mean plasma concentrations of risperidone, 9-hydroxy-risperidone, and prolactin were 4.6, 19.4, and 49.3 ng/ml, respectively.
  
  
  RESULTS
  The oral dose of risperidone correlated significantly with plasma concentrations of risperidone, 9-hydroxy-risperidone, active moiety, and prolactin. The plasma concentration of 9-hydroxy-risperidone, but not of risperidone, correlated significantly with increases in plasma prolactin.
  
  
  CONCLUSIONS
  These data suggest that the 9-hydroxy metabolite plays a predominant role in risperidone's effect on prolactin release.
authors.affiliation: Department of Psychiatry, University Hospital Groningen, the Netherlands. H.Knegtering@psy.umcg.nl
authors.forename: Rikus
authors.initials: R
authors.lastname: Knegtering
authors.forename: Pepijn
authors.initials: P
authors.lastname: Baselmans
authors.forename: Stynke
authors.initials: S
authors.lastname: Castelein
authors.forename: Fokko
authors.initials: F
authors.lastname: Bosker
authors.forename: Richard
authors.initials: R
authors.lastname: Bruggeman
authors.forename: Robert J
authors.initials: RJ
authors.lastname: van den Bosch
mesh_terms: D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000378:metabolism* / Q000493:pharmacokinetics / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D006966:Hyperprolactinemia / Q000097:blood / Q000139:chemically induced* / Q000378:metabolism*; D007555:Isoxazoles / Q000009:adverse effects / Q000378:metabolism* / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D000068882:Paliperidone Palmitate; D011388:Prolactin / Q000097:blood* / Q000378:metabolism; D011618:Psychotic Disorders / Q000097:blood* / Q000188:drug therapy* / Q000378:metabolism; D011743:Pyrimidines / Q000009:adverse effects / Q000378:metabolism* / Q000493:pharmacokinetics*; D018967:Risperidone / Q000378:metabolism* / Q000493:pharmacokinetics / Q000627:therapeutic use
chemical_list: D014150:Antipsychotic Agents; D007555:Isoxazoles; D011743:Pyrimidines; D011388:Prolactin; D018967:Risperidone; D000068882:Paliperidone Palmitate