Adherence to Mood Stabilizers Using a Pharmacy Prescription Database Analysis: Assessment of the Relationship of Non-Adherence to Hospitalization Rates, Cost of Care, and Gender for Patients with Bipolar Type I Disorder

Abstract

Objectives: This study utilized a prescription claims database to retrospectively assess the relationship between adherence rates with a mood stabilizer in bipolar type I patients for: gender, age, psychiatric hospitalization rates, cost of services, and concomitant psychotropic medications. Methods: Adult patients with bipolar type I disorder (N=149; F=92 and M=57) who received at least two prescriptions of a mood stabilizer (i.e., carbamazepine, lamotrigine, lithium, oxcarbazepine, and valproic acid) during a 3-month intake period were included. Adherence to the mood stabilizer was retrospectively analyzed using high: >75% (> 274 days) vs. low: < 75% (< 274 days) supply of a mood stabilizer during 12-months. Results: Only 35.6% of the patients (N=53) met the criteria for > 75% adherence and 11.4% (N=17) met the criteria for > 90% adherence. There was a trend toward women having more days supply of a mood stabilizer compared to men (p=0.08) and older patients having a higher adherence rate with a mood stabilizer (p=0.06). The high adherence group had greater prescription costs (p<0.001) and total cost per year (R2=0.34, p=0.064) and more concomitant medications (p=0.04) than the low adherence group. Overall, there were no significant differences between the high and low adherence groups for mean hospital days, inpatient costs, and total cost of care. Among those patients that were hospitalized there was a negative correlation between adherence and inpatient cost (R2=0.49, p=0.024). Conclusions: Our findings suggest that patients with bipolar type I disorder demonstrate poor medication adherence with a mood stabilizer and that adherence rates based on a prescription claims database using two adherence categories may not be a predictive factor for psychiatric hospitalizations or cost of care.