Objective: In order to develop interventions to optimise methotrexate (MTX) use for the treatment of rheumatoid arthritis (RA) we evaluated the rate of, reasons for and predictors of MTX non-adherence during the first six months of therapy.
Methods: The Rheumatoid Arthritis Medication Study (RAMS) is a prospective multi-centre cohort study of incident MTX users in the UK. Prior to MTX commencement demographic, clinical and psychological data were collected. A weekly patient-completed diary recorded MTX dose, possible side effects and adherence over 26 weeks. The number of non-adherent weeks was calculated. Potential baseline predictors of ever non-adherence (≥1 week non-adherent) during the first six months of MTX therapy were identified using logistic regression analyses.
Results: 606 patients with RA were included; 69% female, mean (SD) age 60 (13) years and DAS28 score 4.2 (1.2). Over the first 6 months following MTX initiation, 158 (26%) patients were ever non-adherent (71% intentional, 19% non-intentional, 10% unexplained) and mean (SD) number of non-adherent weeks was 2.5 (2.1). Multivariable predictors of ever non-adherence included DAS28 (OR 1.1, 95%CI 1.0-1.4), fatigue (OR 1.1, 95%CI 1.0-1.2 per cm), ≥2 comorbidities versus no comorbidities (OR 1.9 95%CI 1.1-3.5) and high medication concerns despite perceived need (OR 1.1, 95%CI 1.0-1.1 per unit decrease in need/concern differential).
Conclusion: This is the largest study evaluating early intentional and non-intentional non-adherence to MTX, which has identified that patient beliefs and multi-morbidity strongly link with non-adherence. These findings can direct the design of and provide potential targets for interventions to improve patient adherence.