Racial differences in medication switching and concomitant prescriptions in the treatment of bipolar disorder

Objective: This study examined whether the practices of switching between classes of medications and prescription of concomitant medications differed between black and nonblack patients with bipolar disorders. Methods: In a retrospective cohort design, data from 1998 to 2004 for patients with diagnoses of bipolar disorders were obtained from a large claims database. Information was obtained on the number of prescriptions for four classes of medications (anticonvulsants, mood stabilizers, and first- and second-generation antipsychotics) as well as on medication switching (between drug classes), concomitant prescriptions, resource use, and outcomes (an emergency department visit or a hospitalization). Logistic models assessed the relationship between outcomes and switching or concomitant prescriptions. Results: The study population consisted of 1,113 adults who received at least one prescription from the four drug classes. Medication switching or concomitant prescriptions were documented for more than one-third of patients (36.6 percent). A significantly greater proportion of black patients received two or more medications from different drug classes (41.1 compared with 34.7 percent). The number of prescriptions was lower for black patients than for nonblack patients. Patients for whom switching or concomitant prescriptions were documented were significantly more likely to have an emergency department visit or a hospitalization, and race was a significant predictor of these outcomes. Conclusions: The prevalence of polypharmacy - medication switching and concomitant prescriptions - was high among patients with bipolar disorder, with a higher prevalence among black patients. Patients who experienced switching or concomitant prescriptions were more likely to visit the emergency department or to be hospitalized.