Better patient persistence with once-daily bupropion compared with twice-daily bupropion.

Evidence suggests that improving adherence and persistence to antidepressant therapy could enhance clinical and economic outcomes in depression. This study was conducted to assess the impact of dosing frequency (once daily with bupropion XL vs twice daily with bupropion SR) on adherence to bupropion therapy in a nationally representative prescription database in the United States. Demographics of patients with a prescription for bupropion XL or bupropion SR between October 1, 2005, and October 31, 2005, were similar between the XL group (n=257,049; 69% female) and the SR group (n=12,468; 67% female). Refill adherence over a 1-year period was greater with bupropion XL than bupropion SR. The percentage of patients with >or=1 refill over 1 year was 60.1% with bupropion XL compared with 51.3% with bupropion SR (P < 0.0001). The percentage of patients with >or=6 refills over 1 year was 25.3% with bupropion XL compared with 9.5% with bupropion SR. Bupropion XL was associated with significantly greater likelihood of refilling a prescription than bupropion SR as shown by Kaplan-Meier curves (P < 0.0001, log-rank test). The medication possession ratio over a 9-month period was higher for bupropion XL (0.26) than it was for bupropion SR (0.16). Logistic regression analyses show that patients with a prescription for bupropion SR were significantly less likely to fill a future prescription than were patients with a prescription for bupropion XL. These data show that adherence to bupropion therapy in this sample was better with the once-daily XL formulation than with the twice-daily SR formulation across several measures.