Poor antipsychotic adherence among patients with schizophrenia: medication and patient factors.

Many patients with schizophrenia are poorly adherent with antipsychotic medications. The newer, atypical antipsychotics may be more acceptable to patients and result in increased adherence. We used national Department of Veterans Affairs (VA) pharmacy data to examine whether patients receiving atypical agents are more adherent with their medication and explored patient factors associated with adherence. Patients who received a diagnosis of schizophrenia or schizoaffective disorder between October 1, 1998, and September 30, 1999, were identified in the VA National Psychosis Registry. We calculated medication possession ratios (MPRs) for patients filling prescriptions for one (n = 49,003) or two (n = 14,211) antipsychotics during the year. We examined cross-sectional relationships among adherence, type of antipsychotic, and patient characteristics and explored adherence among patients switching antipsychotics during the year. Among patients receiving one antipsychotic, 40 percent had MPRs < 0.8, indicating poor adherence. African-Americans and younger patients were more likely to be poorly adherent. Cross-sectionally, patients on atypical agents were more likely to be poorly adherent (41.5%) than patients on conventional agents (37.8%). However, among a small group of patients switching from a conventional to an atypical agent (n = 1,661) during the year, the percentage who were poorly adherent decreased from 46 percent to 40 percent. We describe the continuum of antipsychotic adherence among a large sample of patients with schizophrenia and confirm that poor adherence is common. African-Americans and younger patients are particularly at risk. Unfortunately, atypical antipsychotics may not be associated with substantial improvements in adherence. More intensive interventions are likely needed.