Analysis of healthcare utilization patterns and adherence in patients receiving typical and atypical antipsychotic medications

Objective: To examine the effects of typical and atypical antipsychotics on medication adherence and healthcare resource utilization. Research design and methods: This was a retrospective observational cohort analysis of pharmacy and medical health insurance reimbursement data of patients from a southeastern United States health plan. Pharmacy data of subjects between 6 and 65 years of age were identified. Inclusion criteria included initiation of a single antipsychotic agent between July 1, 1999 and September 30, 2000; no antipsychotic medication usage 6 months prior to the index prescription date; and continuous health plan enrollment for the 18-month study period. Multivariable methods were utilized to analyze healthcare resource utilizations between groups. Outcome measures: Primary outcome measures included: (1) adherence and persistence with antipsychotic therapy; (2) healthcare utilization for outpatient office and hospital visits, inpatient hospital visits, and emergency room visits; and (3) therapy modifications and concomitant medications. Results: A total of 469 patients met initial study criteria. Atypical and typical antipsychotics were prescribed to 384 and 85 patients, respectively. Length of therapy (days) for the atypical cohort was significantly longer (136 vs 80; p < 0.001). As defined using medication possession ratio (MPR), the atypical cohort was significantly more adherent to therapy than the typical cohort (mean MPR, 0.53 vs 0.24; p < 0.001). After adjusting for differences in demographics, baseline utilization, MPR, and length of therapy (n = 377), the atypical cohort experienced significantly fewer office visits (2,635 vs 4,249 per 1000 patients per month [P1000PPM]; p = 0.005), fewer inpatient admissions (197 vs 511 P1000PPM; p = 0.032), and fewer emergency room visits (125 vs 354 P1000PPM; p = 0.002). Conclusions: Atypical antipsychotic users were significantly more adherent to therapy, and had lower rates of office, hospital and emergency room utilization. Within the context of inherent limitations associated with health insurance claims databases, this study suggests that a relationship exists across cohorts between medication adherence and use of healthcare resources.