title: Relationship between initial quetiapine dose and effectiveness as reflected in subsequent mental health service use among patients with schizophrenia or bipolar disorder.
abstract: OBJECTIVE
  To investigate the association between initial quetiapine dose and effectiveness as gauged by subsequent use of mental health services.
  
  
  METHODS
  Using a health plan database, we identified patients with bipolar disorder or schizophrenia treated with quetiapine monotherapy for at least four consecutive months. The stability of each patient before and after quetiapine treatment was measured by use of mental health services other than antipsychotic drug, measured primarily by charges reported on claims. Regression models controlling for patient differences measured associations between initial quetiapine dose and subsequent mental health service use.
  
  
  RESULTS
  Commercially insured patients with schizophrenia (n = 581) or bipolar disorder (n = 2421) received quetiapine monotherapy at mean (SD) initial daily doses of 237 (198) mg and 147 (171) mg, respectively. Both groups showed negative associations between initial daily dose and subsequent mental health charges. Among patients with schizophrenia, mental health charges decreased by US 1.28 dollars for each additional milligram of quetiapine (P = 0.1097). Among patients with bipolar disorder, there was a significant decrease of US 1.31 dollars per additional milligram of quetiapine (P = 0.0484). For schizophrenia, hospitalizations were reduced by 0.4% for each additional milligram of quetiapine (P = 0.0189). For bipolar disorder, the association between quetiapine dose and outpatient charges was negative and trended toward significance (P = 0.074), showing a US 0.54 dollars reduction in these charges for each additional milligram of quetiapine; the association with hospitalization was not significant.
  
  
  CONCLUSIONS
  In patients with schizophrenia or bipolar disorder, higher initial doses of quetiapine may be more effective in stabilizing patients as reflected in lower subsequent mental health service use.
authors.affiliation: HECON Associates, Inc., Montgomery Village, MD 20886, USA. heconassoc@aol.com
authors.forename: Frank
authors.initials: F
authors.lastname: Gianfrancesco
authors.forename: Ruey-hua
authors.initials: RH
authors.lastname: Wang
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Pesa
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000008:administration & dosage* / Q000191:economics / Q000494:pharmacology; D001714:Bipolar Disorder / Q000188:drug therapy*; D003987:Dibenzothiazepines / Q000008:administration & dosage* / Q000191:economics / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D017048:Health Care Costs; D006801:Humans; D016013:Likelihood Functions; D016015:Logistic Models; D008297:Male; D008605:Mental Health Services / Q000706:statistics & numerical data*; D000069348:Quetiapine Fumarate; D012559:Schizophrenia / Q000188:drug therapy*; D016896:Treatment Outcome; D014481:United States
chemical_list: D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D000069348:Quetiapine Fumarate