Adherence to Antipsychotic Drugs for Patients with Schizophrenia

Philadelphia—Patients who adhere to their antipsychotic medications are less likely to be hospitalized and spend less time in the hospital when admitted, according to a retrospective database analysis. The inverse relationship between adherence and hospitalization rates and length of stay occurred for Medicare and non-Medicare populations.

The authors presented the results at the APA meeting in a poster session. The poster was titled Antipsychotic Drug Adherence Correlates with Hospitalization Rates and Length of Stay Among Medicare and Non-Medicare Schizophrenia Populations.

Patient adherence to antipsychotic medications depends on several factors, among them the disease state and tolerance to available therapies. In this study, the authors scanned the Thomson Reuters MarketScan^® Research Databases, both commercial and Medicare, for patients with schizophrenia who began taking oral antipsychotics between January 1, 2005, and September 30, 2010.

Patients were included if they were ≥13 years of age when they initiated antipsychotic treatment, had ≥1 inpatient or ≥2 outpatient visits on separate dates with a primary or secondary diagnosis of International Classification of Diseases, Ninth Revision, Clinical Modification code 295 during the baseline period, and had ≥12 months of continuous medical and prescription drug coverage before beginning antipsychotic treatment.

The authors identified 1462 non-Medicare patients and 354 Medicare patients who met the criteria. The most common antipsychotics prescribed were risperidone, aripiprazole, and quetiapine.

Of the non-Medicare patients, 50% were female, and the mean age was 39.1 years. The mean age of the Medicare patients was 71.4 years, and 65% were female. The mean Charlson Comorbidity Index score was 1.77 in the Medicare group compared with 0.50 in the non-Medicare group (P<.05).

The authors assessed medication adherence using the medication possession ratio (MPR), calculated as the total number of days of drug supply during the follow-up period (12 months after patients started treatment) divided by the total number of days in the follow-up period. Patients who had MPR ≥0.7 were allocated to the high-adherence cohort, while those with MPR <0.7 were grouped into the low-adherence cohort.

During the first year after starting treatment, the mean MPR was 0.43 in the non-Medicare group and 0.49 in the Medicare group. The mean rate of hospitalizations for schizophrenia was 0.23 hospitalizations per patient year in the non-Medicare group and 0.18 in the Medicare group.

For patients in the non-Medicare group, an increased MPR was associated with a significantly lower hospitalization rate (P=.011) and a significantly shorter length of stay in the hospital (P=.018). Among Medicare patients, better adherence to the medications was associated with significantly fewer hospitalizations (P=.044) and a significantly shorter length of stay in the hospital (P=.021).

The authors concluded that clinicians who focus on improving adherence can contribute to lowering healthcare costs. However, antipsychotic medications have side effects that can cause patients to stop taking them. The authors suggested healthcare professionals monitor and attempt to manage side effects, leading to improved adherence, a reduction on the burden to patients, and less utilization of healthcare resources.

This study was supported by Otsuka America, Inc.