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.