Antipsychotic polypharmacy and high-dose prescription in schizophrenia: a 5-year comparison

The co-prescription of multiple antipsychotic drugs continues to increase despite a lack of evidence supporting this practice. The purpose of this study was to quantify and describe recent trends of antipsychotic polypharmacy in Korean schizophrenic inpatients by comparing prescribed medications between the years of 2005 and 2010.

We reviewed comprehensive medication profiles of schizophrenic patients discharged from a university psychiatric hospital in 2005 (n=194) or 2010 (n=201). Antipsychotic polypharmacy was defined as the concurrent receipt of two or more chemically distinct antipsychotics for at least 14 days. High antipsychotic dose was defined as a prescribed daily dose to defined daily dose ratio of greater than 1.5.

Antipsychotic polypharmacy increased between 2005 (37.1%) and 2010 (48.3%, p=0.025). The most frequently used drug within combinations of antipsychotics was haloperidol in 2005 (51.4%) and quetiapine in 2010 (48.5%). Overall, no changes were observed between 2005 and 2010 in the rate of prescribing high-dose antipsychotics. High-dose antipsychotic monotherapy decreased across years (from 30.4 to 18.4%), but high-dose antipsychotic polypharmacy increased (from 34.0 to 45.3%). Regression analysis revealed that antipsychotic polypharmacy was strongly associated with high doses of prescribed antipsychotics (odds ratio=18.60, p<0.001).

The practice of prescribing multiple antipsychotics to patients with schizophrenia is increasing, and high-dose antipsychotic drugs are more likely to be prescribed in combination than in isolation. The reasons for this pattern of prescription and its impact warrants further study.