Medication adherence and attrition to biologic treatment in rheumatoid arthritis patients.

Purpose: The objectives of this study were to assess medication adherence rate and attrition rate in first-time adalimumab (ADA) or etanercept (ETA) users in rheumatoid arthritis (RA) patients. This study also identified the risk factors associated with nonadherence and treatment abandonment.

Methods: This was a retrospective study with a 2-year follow-up. A total 2151 adult RA patients (18 years of age and older) who initiated ADA or ETA treatment in the Kaiser Permanente Southern California health plan between 2002 and 2009 were identified. Among those on treatment in the first year, continuous treatment receipt was determined by having at least 1 medication refill in the second year; otherwise treatment was considered as abandoned. Medication adherence was measured through proportion of days covered (PDC) and compared between patients continuously on treatment and those abandoning treatment. Risk factors of nonadherence (PDC <80%) and treatment abandonment were estimated by a multinomial logistic regression model.

Findings: Patients who abandoned treatment had significantly lower PDC (37.3%) and lower average number of refills (5.1) than adherers (PDC = 88.8%; average number of refills = 12.4) and nonadherers (PDC = 53.3%; average refills = 8.2). Age, African Americans (odds ratio [OR], 1.49; 95% CI, 1.03-2.17), corticosteroids use (OR, 0.80; 95% CI, 0.63-0.98), and history of physical/occupational therapy (OR = 0.66; 95% CI, 0.46-0.93) were associated with nonadherence, whereas having a comorbidity (OR, 1.24; 95% CI, 1.01-1.57) was associated with treatment abandonment. The difference in PDC between ADA and ETA was no longer statistically significant after excluding the treatment abandonment group. A higher proportion of ADA users abandoned treatment than ETA users (42.9% vs 32.2%).

Implications: Taking into account treatment abandonment when measuring medication adherence in ADA and ETA use in RA patients can provide a fair and clinically meaningful view of patients' medication-taking behavior.