title: Age and gender effects on olanzapine and risperidone plasma concentrations in children and adolescents.
abstract: BACKGROUND
  Risperidone and olanzapine are second-generation antipsychotics that are increasingly used in child and adolescent psychiatry. So far, little is known about plasma concentrations and concentration-to-dose (C/D) ratios of these agents in children and adolescents compared to adults.
  
  
  METHODS
  This study investigated whether age and gender influence risperidone and olanzapine plasma concentration by determining risperidone and olanzapine plasma levels by tandem mass spectrometry in 162 Caucasian patients (98 risperidone and 64 olanzapine).
  
  
  RESULTS
  For risperidone and 9-hydroxyrisperidone, the C(total)/D ratio was almost identical in both age groups (10-18 and 19-45 years, respectively). In the younger age group, females exhibited significantly higher total plasma levels than males while receiving similar doses of risperidone. For olanzapine, in adolescents significantly higher C/D ratios were detected by an average of 43% (after adjustment for weight: 34%) compared to adults.
  
  
  CONCLUSIONS
  This study demonstrates an age effect for olanzapine but not for risperidone resulting in higher olanzapine plasma levels in younger patients. For risperidone, we found a gender effect as female adolescent patients had significantly higher risperidone plasma concentrations than male adolescent patients. Future prospective studies are necessary to clarify whether the prescribed dosage should be different in young and older patients.
authors.affiliation: Department of Psychiatry and Psychotherapy, Private Medical University Salzburg, Ignaz Harrer Strasse 79, Salzburg, Austria. w.aichhorn@salk.at
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Aichhorn
authors.forename: Josef
authors.initials: J
authors.lastname: Marksteiner
authors.forename: Thomas
authors.initials: T
authors.lastname: Walch
authors.forename: Gerald
authors.initials: G
authors.lastname: Zernig
authors.forename: Hartmann
authors.initials: H
authors.lastname: Hinterhuber
authors.forename: Christoph
authors.initials: C
authors.lastname: Stuppaeck
authors.forename: Georg
authors.initials: G
authors.lastname: Kemmler
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000378:metabolism; D018692:Antimanic Agents / Q000009:adverse effects; D014150:Antipsychotic Agents / Q000097:blood*; D001569:Benzodiazepines / Q000097:blood*; D001835:Body Weight / Q000502:physiology; D002648:Child; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077152:Olanzapine; D011618:Psychotic Disorders / Q000097:blood; D012189:Retrospective Studies; D018967:Risperidone / Q000097:blood*; D012727:Sex Characteristics; D012907:Smoking / Q000378:metabolism; D053719:Tandem Mass Spectrometry; D014635:Valproic Acid / Q000009:adverse effects
chemical_list: D018692:Antimanic Agents; D014150:Antipsychotic Agents; D001569:Benzodiazepines; D014635:Valproic Acid; D018967:Risperidone; D000077152:Olanzapine