Adherence, persistence of use, and costs associated with second-generation antipsychotics for bipolar disorder.

OBJECTIVE: A retrospective study using Medicaid claims identified patients with bipolar disorder for whom oral second-generation antipsychotics were prescribed and compared rates of adherence, persistence of use, and costs across five groups of patients taking aripiprazole, olanzapine, quetiapine, risperidone, or ziprasidone. METHODS: Medicaid claims data for 2,446 bipolar patients were analyzed from eight states. The 18-month observation period included the six months before and the 12 months after the index prescription date. Adherence was defined as a medication possession ratio >80%. Persistence of use was measured by the number of days of medication therapy before a 30-day gap. Mental health-related prescription costs, total prescription costs, total mental health-related costs, and total costs were assessed. Ziprasidone was the comparator. RESULTS: Clinically recommended doses of second-generation antipsychotic medications were prescribed for 45% of the patients (N = 1,102). Of these, 58% (N = 642 of 1,102) were adherent with the prescribed medication, with no significant differences between medication groups. Median time to nonpersistence of use averaged 96 days. Patients taking olanzapine were about 35% more likely than patients taking ziprasidone to discontinue taking their medication (hazard ratio = 1.34, 95% confidence interval = 1.02-1.76, p = .04). Mental health-related prescription costs and total prescription costs were lower for risperidone than ziprasidone. No statistically significant differences were found between the groups for all mental health-related costs or total costs. CONCLUSIONS: Among patients in a sizeable Medicaid cohort for whom a second-generation antipsychotic medication was prescribed, less than half had a clinically recommended dose, and less than two-thirds with a clinically recommended dose were adherent to the medication, confirming that many patients with bipolar disorder do not receive clinically recommended doses of second-generation antipsychotics.