OBJECTIVES : Though biologic disease modifying anti-rheumatic drugs (bDMARDs) have shown higher efficacy and better tolerance in clinical trials than conventional disease modifying anti-rheumatic drugs (cDMARDs), their cost could potentially affect patient adherence. The objective of this study was to estimate adherence to bDMARDs and cDMARDs in patients with Rheumatoid Arthritis (RA), and to assess if adherence is associated with DMARD type (bDMARDs vs cDMARDs) or patient out-of-pocket (OOP) costs.

METHODS : Patients with RA from the 2008-2012 Medicare Current Beneficiary Survey (MCBS) data with at least 2 Medicare Part D claims for DMARDs were included. Medication adherence was calculated as proportion of days covered (PDC) in six-month period following date of first DMARD fill. Individuals with PDC>=0.80 were considered adherent. Total OOP medication costs per patient were generated as a sum of OOP costs per claim. Logistic regression was used to assess associations between adherence and DMARD type and OOP costs.

RESULTS :