Persistent antipsychotic polypharmacy and excessive dosing in the community psychiatric treatment setting: a review of medication profiles in 435 Canadian outpatients.
OBJECTIVE
The present study aimed (1) to determine the proportion of patients treated with persistent antipsychotic polypharmacy in an outpatient population and (2) to determine if persistent antipsychotic polypharmacy is associated with excessive dosing.


METHODS
Using a province-wide network that links all pharmacies in British Columbia, Canada, to a central set of data systems, we identified community mental health outpatients who had been treated with the same pharmacologic regimen for at least 90 days. Apart from antipsychotics, data collection included anticholinergics, antidepressants, mood stabilizers, benzodiazepines, lipid-lowering agents, and antidiabetic agents. Demographic data including sex, age, and diagnosis were obtained from the patient's chart. In order to compare dosages of the various antipsychotics we used a fixed unit of measurement based on dividing the prescribed daily dose (PDD) by the defined daily dose (DDD). A PDD/DDD ratio greater than 1.5 was defined as excessive dosing.


RESULTS
Four hundred thirty-five patients met the inclusion criteria and were included in the analysis. Overall, the prevalence of persistent antipsychotic polypharmacy was 25.7% for the entire cohort. The prevalence of persistent antipsychotic polypharmacy was highest for patients with schizoaffective disorder (33.7%), followed by schizophrenia (31.7%), psychosis not otherwise specified (20.0%), bipolar disorder (16.9%), and major depression (14.3%). The mean +/- SD PDD/DDD ratio for all patients prescribed persistent antipsychotic polypharmacy was not only excessive, it was significantly greater compared to that of patients receiving antipsychotic monotherapy (1.94 +/- 0.12 vs 0.94 +/- 0.04, P < .005).


CONCLUSIONS
Using a diagnostically heterogeneous outpatient population, this study is, we believe, the first to report that persistent antipsychotic polypharmacy is associated with excessive dosing, in and of itself as well as compared to antipsychotic monotherapy.
Procyshyn
Ric M
RM
British Columbia Mental Health & Addictions Research Institute, A3-113, 938 W 28th Ave, Vancouver, British Columbia, Canada, V5Z 4H4. rprocyshyn@bcmhs.bc.ca
Honer
William G
WG
Wu
Tony K Y
TK
Ko
Rebecca W Y
RW
McIsaac
Sean A
SA
Young
Allan H
AH
Johnson
Joy L
JL
Barr
Alasdair M
AM
D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001714:Bipolar Disorder / Q000188:drug therapy; D001955:British Columbia; D003865:Major Depressive Disorder / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D008485:Medical Audit; D008508:Medication Errors / Q000706:statistics & numerical data*; D001523:Mental Disorders / Q000188:drug therapy*; D008875:Middle Aged; D010045:Outpatients; D019338:Polypharmacy; D015995:Prevalence; D011618:Psychotic Disorders / Q000188:drug therapy; D012559:Schizophrenia / Q000188:drug therapy
D014150:Antipsychotic Agents