title: Association of antipsychotic polypharmacy with health service cost: a register-based cost analysis.
abstract: OBJECTIVE
  To investigate the association of antipsychotic polypharmacy in schizophrenia with cost of primary and secondary health service use.
  
  
  METHODS
  Comparative analysis of health service cost for patients prescribed antipsychotic polypharmacy versus antipsychotic monotherapy. Resource utilisation and costs were described using central Danish registers for a 2 year period (2007-2008). We included patients attached to one of two Danish psychiatric referral centres in 1 January 2008 and/or 1 January 2009. Their prescribed treatment with either antipsychotic polypharmacy or monotherapy at the two cross-sectional dates was recorded and used as proxy of polypharmacy exposure during the preceding year. A multivariate generalised linear model was fitted with total costs of primary and secondary health service use as dependent variable, and antipsychotic polypharmacy, diagnosis, age, gender, disease duration, psychiatric inpatient admissions, and treatment site as covariates.
  
  
  RESULTS
  The sample consisted of 736 outpatients with a diagnosis in the schizophrenia spectrum. Antipsychotic polypharmacy was associated with significantly higher total health service costs compared with monotherapy (2007: 25% higher costs; 2008: 17% higher costs) when adjusting for potential confounders and risk factors. A subgroup analysis suggested that the excessive costs associated with antipsychotic polypharmacy were partly accounted for by the functional level of the patients.
  
  
  CONCLUSIONS
  The results demonstrate that antipsychotic co-prescribing is associated with increased use of health care services, even though no causal relations can be inferred from an observational study.
authors: Centre for Neuropsychiatric Schizophrenia Research, Copenhagen University Hospital, Mental Health Services - Capital Region of Denmark, Glostrup, Nordre Ringvej 29-67, 2600 Glostrup, Denmark. lone.baandrup@regionh.dk
authors: Lone
authors: L
authors: Baandrup
authors: Jan
authors: J
authors: Sørensen
authors: Henrik
authors: H
authors: Lublin
authors: Merete
authors: M
authors: Nordentoft
authors: Birte
authors: B
authors: Glenthoj
mesh_terms: D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000191:economics / Q000627:therapeutic use*; D016001:Confidence Intervals; D003362:Cost-Benefit Analysis; D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D017048:Health Care Costs / Q000706:statistics & numerical data*; D019538:Health Care Surveys; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010045:Outpatients / Q000706:statistics & numerical data; D019338:Polypharmacy; D012042:Registries; D012189:Retrospective Studies; D012559:Schizophrenia / Q000188:drug therapy / Q000191:economics*; D055815:Young Adult
chemical_list: D014150:Antipsychotic Agents