Impact of Antipsychotic Drug Adherence on the Management of Schizophrenia Among US Medicare Patients
Dario Mirski, MD; Steve Offord, PhD; Bruce Wong, MD; Jay Lin, PhD; and Ross Baker, PhD
From Otsuka America Pharmaceutical, Inc, Princeton, New Jersey (Drs Mirski and Offord); the University of Pennsylvania, Philadelphia, Pennsylvania (Dr Wong); Novosys Health, Flemington, New Jersey (Dr Lin); and Otsuka Pharmaceutical Development and Commercialization, Inc, Princeton, New Jersey (Dr Baker).
This poster presentation was supported by Otsuka America Pharmaceutical, Inc.
Background: Treatment of schizophrenia patients is complicated by drug non-adherence. This study examined the impact of antipsychotic drug adherence on the healthcare usage among Medicare patients with schizophrenia.
Methods: Schizophrenic patients, identified by ICD-9 codes from the MarketScan Medicare claims database from 1/1/2005 to 9/30/2010, were required to have ≥12 months of continuous coverage before and after (follow-up) earliest antipsychotic use. Drug adherence was estimated by medication possession ratio (MPR). High adherence (HA) was defined as a follow-up period MPR ≥0.7; a MPR <0.7 indicated low adherence (LA). Follow-up period healthcare usage was assessed.
Results: 354 patients were identified, 228 (64%) had LA and 126 (36%) had HA with mean ± standard deviation MPRs of 0.24±0.19 and 0.94±0.09, respectively. LA patients had a greater number of hospitalizations (0.68 vs. 0.44; p=0.02) with a longer length of stay (LOS) (7.0 vs. 2.6 days; p=0.005), more schizophrenia-related inpatient services (18.9% vs. 10.3%; p=0.04) and a greater number of schizophrenia relapse hospitalizations (0.22 vs. 0.11; p=0.03) with significantly longer LOS (3.2 vs. 0.7 days; p=0.03). HA patients had a greater number of pharmacy claims (72.97 vs. 49.54; p<0.001) and use of schizophrenia-related medications (11.13 vs. 4.57; p<0.001). After adjusting for major patient characteristics with Generalized Linear Model, high adherence was associated with fewer any-cause hospitalizations (p<0.001) and shorter LOS (p<0.001).
Conclusions: Schizophrenia patients in Medicare have poor adherence to antipsychotics. Patients with low medication adherence vs. high adherence are associated with lower use of schizophrenia-related medication, but more inpatient care and longer LOS.
Poor antipsychotic medication adherence is common among Medicare schizophrenia patients
Poor antipsychotic medication adherence is associated with increased healthcare resource usage
Ascher-Svanum H, Zhu B, Faries DE, et al. Medication adherence levels and differential use of mental-health services in the treatment of schizophrenia. BMC Res Notes. 2009;2:6. PubMed
Khaykin E, Eaton WW, Ford DE, et al. Health insurance coverage among persons with schizophrenia in the United States. Psychiatr Serv. 2010;61(8):830–834. PubMed