Association between antipsychotic combination therapy and treatment adherence among individuals with bipolar disorder

BACKGROUND: This study investigated the effect on antipsychotic treatment adherence of combining quetiapine or risperidone with lithium, anticonvulsants, and/or antidepressants among bipolar individuals with predominantly manic/mixed or depressive symptoms.

METHODS: Treatment episodes with quetiapine or risperidone were identified from individuals with medical claims for bipolar/manic disorder. Multiple regression analysis was used to evaluate the impact of antipsychotic combinations on treatment adherence, as measured by intensity (medication possession ratio [MPR]) and treatment duration.

RESULTS: Among mixed/manic individuals, combination therapies were associated with lower antipsychotic MPRs than monotherapy (P< .05), with MPR decreasing with number of medications. Quetiapine showed a similar pattern among depressed individuals, whereas risperidone showed a weaker association. For both subgroups, antipsychotic combinations with anticonvulsants were associated with lower MPRs than combinations with lithium. For manic/mixed individuals, combining quetiapine with an anticonvulsant and lithium was associated with shorter treatment durations than quetiapine alone (P <or= .05). For manic/mixed individuals receiving risperidone, treatment duration was not affected by type of combination therapy. Among depressed subgroups, treatment duration was unrelated to combination therapy.

CONCLUSIONS: Adherence to quetiapine and risperidone may be affected by whether they are prescribed alone or as combination therapy, the combination strategy, and the predominant symptomatology of the individual.