Background/Purpose: Medication adherence to biologic DMARDs has been associated with optimal clinical outcomes. Adherence varies with primary dispensing channel among rheumatoid arthritis patients. Prior studies have primarily focused on individual inflammatory conditions. This research compared adherence among patients diagnosed with rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis or a combination of these conditions over a two-year follow-up period by primary dispensing channel.

Methods: A retrospective cohort analysis of patients continuously eligible for pharmacy/medical benefits, with biologic DMARD claims and corresponding diagnoses for rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis or a combination of these diagnoses. Dispensing channel was determined by a threshold of 75% of biologic DMARD therapy through a 2-year follow-up period. Adherence was calculated using medication possession ratio during each 1-year period of analysis. Adherent patients were defined as those whose biologic DMARD adherence was at least 80%. Patients were classified as new or continuous users based on 6 months prior to index biologic DMARD claim. Patients were matched between channels based on age, gender, new or continuous use, and diagnosed condition using propensity score matching. Logistic regression was used to assess impact of dispensing channel and to control for age, gender, new or continuous use, diagnosed condition, and comorbidity burden in year one. Year two adherence results also controlled for year one adherence behavior.

Results: Final sample included 2,436 patients on biologic DMARD therapy meeting selection criteria, with an index prescription between July 1 and December 31, 2015. Likelihood of adherence was found to be significantly lower during the first year of follow-up among patients primarily filling their biologic DMARD through retail compared to specialty pharmacy (37.6% [95% CI: 23.7%-48.9%] lower compared to our specialty pharmacy, and 29.0% [95% CI: 10.6%-43.7%] lower compared to other specialty pharmacy). Average adherence, based on MPR, was lower in the second year for all channels, and no significant difference in the change in average adherence was found (p >0.05). Likelihood of adherence in the second year of analysis was influenced by adherence behavior in the first year, with adherent patients in the first year being 11 times more likely to be adherent in the second year (aOR=11.18, 95% CI: 9.09-13.73).

Conclusion: Among patients with diverse inflammatory condition diagnoses, those using specialty pharmacy as primary dispensing channel for biologic DMARDs have higher adherence in the first year of measurement after controlling for other factors influencing adherence. Adherence in the second year was lower for all channels; however, dispensing channel does not appear to impact the magnitude of change in adherence between years. Given that the largest single predictor of adherence in the second year is prior adherence, choice of primary dispensing channel during the first year of therapy should be considered upon starting or continuing biologic DMARD therapy for patients with inflammatory conditions.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/adherence-to-biologic-disease-modifying-anti-rheumatic-drugs-dmards-a-comparison-of-long-term-adherence-among-patients-with-various-inflammatory-conditions-by-primary-dispensing-channel/