title: Is the Defined Daily Dose system a reliable tool for standardizing antipsychotic dosages?
abstract: The present study was carried out to establish whether the Defined Daily Doses (DDDs) system could be reliably applied to standardize antipsychotic dosages. Initially, the relationship between antipsychotic doses expressed as DDDs, chlorpromazine equivalents (CPZEs) and percentages of the British National Formulary (BNF) maximum recommended daily dose were investigated by calculating Spearman's rank correlation coefficients. Second, factors associated with antipsychotic dose, expressed as DDDs, CPZEs and percentages of the BNF maximum recommended daily dose, were investigated by means of linear regression analysis. The study sample consisted of 277 patients with schizophrenia. The relationship between antipsychotic daily doses expressed as multiples of DDDs and CPZEs revealed a significant correlation (Spearman's rho=0.779, P<0.001). Similarly, the relationship between antipsychotic daily doses expressed as multiples of DDDs and percentages of the BNF maximum recommended daily dose revealed a significant correlation (Spearman's rho=0.869, P<0.001). Linear regression analyses highlighted a high degree of coherence between antipsychotic doses expressed as DDDs, CPZEs and percentages of the BNF maximum recommended daily dose. In conclusion, this study found that the DDD system is a reliable tool for standardizing antipsychotic doses in drug utilization research.
authors.affiliation: Department of Medicine and Public Health, Section of Psychiatry and Clinical Psychology, University of Verona, Italy. michela.nose@univr.it
authors.forename: Michela
authors.initials: M
authors.lastname: Nosè
authors.forename: Michele
authors.initials: M
authors.lastname: Tansella
authors.forename: Graham
authors.initials: G
authors.lastname: Thornicroft
authors.forename: Aart
authors.initials: A
authors.lastname: Schene
authors.forename: Thomas
authors.initials: T
authors.lastname: Becker
authors.forename: Antonio
authors.initials: A
authors.lastname: Veronese
authors.forename: Morven
authors.initials: M
authors.lastname: Leese
authors.forename: Maarten
authors.initials: M
authors.lastname: Koeter
authors.forename: Matthias
authors.initials: M
authors.lastname: Angermeyer
authors.forename: Corrado
authors.initials: C
authors.lastname: Barbui
mesh_terms: D014150:Antipsychotic Agents / Q000008:administration & dosage* / Q000627:therapeutic use*; D002746:Chlorpromazine / Q000008:administration & dosage / Q000627:therapeutic use; D004363:Drug Utilization; D006801:Humans; D016014:Linear Models; D011618:Psychotic Disorders / Q000188:drug therapy* / Q000523:psychology; D016032:Randomized Controlled Trials as Topic; D012959:Socioeconomic Factors
chemical_list: D014150:Antipsychotic Agents; D002746:Chlorpromazine