Antipsychotic polypharmacy: a Japanese survey of prescribers' attitudes and rationales.

While combining antipsychotics is common in schizophrenia treatment, the literature on the reasons for antipsychotic polypharmacy (APP) is limited. We aimed to identify prescriber attitudes and rationales for APP in Japan where high APP utilization is reported. Two-hundred and seventeen psychiatrists participated in the survey, which assessed APP attitudes and behaviors. Prescribing APP to 47.7±24.7% (mean±S.D.) of their patients, psychiatrists reported that they were "moderately" concerned about APP. The most APP-justifiable factors were (1="not at all" to 5="extreme") cross titration (4.50±0.67), randomized controlled evidence (3.67±0.83), and treatment of comorbid conditions (3.31±0.83). Conversely, APP-discouraging factors were chronic side effects (4.14±0.64), difficulty determining cause and effect (4.07±0.74), and acute side effects (3.99±0.81). Comparing high to low APP prescribers (>50% vs. ≤50% of patients), no differences emerged regarding APP justification and concerns. In multivariate analyses, high APP use was associated with practice at a psychiatric hospital (OR: 2.70, 95% CI: 1.29-5.67, p=0.009), concern about potential drug-drug interactions (OR: 1.56, 95% CI: 1.04-2.35, p=0.031), and less reliance on case reports of APP showing efficacy (OR: 0.64, 95% CI: 0.44-0.92, p=0.017) (r(2)=0.111, p=0.001). High and low APP prescribers shared a comparable degree of justifications and concerns. Future research should examine the impact of cultural determinants on APP.