Self-injectable TNF inhibitors are increasingly used early in the chronic treatment of moderate to severe rheumatologic conditions. We estimated medication adherence/persistence over time following initiation in young adult and older adult patients with rheumatoid arthritis, ankylosing spondylitis or psoriatic arthritis.
We conducted a retrospective cohort study of patients aged 18+ years newly initiating etanercept, adalimumab, certolizumab pegol, or golimumab using the Truven Health MarketScan Database between 2009 and 2013. Pharmacy dispensing data were used to calculate 12-month medication possession ratios (MPR) and determine adherence (MPR ≥ 0.80) for up to 3 years after starting therapy. Persistence over each 12-month interval was defined as not having a ≥92-day treatment gap. Multivariable generalized estimating equation models were used to calculate odds ratios (OR) and robust 95% confidence intervals (CI) for associations between patient characteristics and repeated adherence/persistence measures over time.
Among 53,477 new users, 14% were young adults (18-34 years), 49% middle-aged (35-54 years), and 37% older adults (55+ years). Overall, 37% of patients were adherent and 83% were persistent in the first year of therapy. The lowest adherence (17%) and persistence (70%) were observed among young adult patients by Year +3. Compared to older adults, middle-aged (OR = 0.73, 95% CI: 0.71-0.76) and young adults (OR = 0.50, 95% CI: 0.47-0.53) were less likely to be adherent. Higher Charlson comorbidity scores, hospitalizations, and emergency department visits were associated with non-adherence/non-persistence.
We observed low adherence to self-administered TNF inhibitors but most patients remained persistent over time. Further efforts to improve adherence in young adults and patients with greater comorbidity are needed.