Description of long-term polypharmacy among schizophrenia outpatients.
This large nationwide study describes the prevalence and predictors of long-term antipsychotic polypharmacy among patients with schizophrenia. A register-based longitudinal study of all people in Finland, who had at least one hospitalization due to schizophrenia during the years 2000-2007 and who were alive on March 1, 2007. Entry to the cohort was defined from the first hospitalization for schizophrenia during the years 2000-2007, and the date of assessment of antipsychotic polypharmacy was March 1, 2007. We studied separately chronic (N = 8,037) and recent onset (N = 8,046) schizophrenia patients. Antipsychotic polypharmacy was defined as overlapping of two or more filled prescriptions of antipsychotics for over 60 days. In a total 16,083 patients with schizophrenia the prevalence of antipsychotic polypharmacy was 46.2 % (N = 7,436, mean age 47.5 years, male 55 %). The longer the duration of schizophrenia, the more common the antipsychotic polypharmacy. Long index hospitalization and being male significantly associated with antipsychotic polypharmacy among all schizophrenia patients. Especially, in chronic schizophrenia patients, the previous use of benzodiazepine like agents was associated with antipsychotic polypharmacy, but the use of antidepressants associated with less frequent antipsychotic polypharmacy. Antipsychotic polypharmacy was widely prevalent among patients with schizophrenia and it was associated with long hospitalizations and long duration of illness. Benzodiazepine use was associated with increased risk and antidepressant use with decreased risk of antipsychotic polypharmacy when the effect of other clinical and socioeconomic factors was adjusted. Research is needed of risks and benefits of antipsychotic polypharmacy and augmentation of antipsychotic with other psychoactive drugs.