Nonadherence is a major concern for patients with rheumatoid arthritis (RA) receiving biological disease-modifying agents, which are intended to slow the progression of the disease. The medication-possession ratio, which is a measurement of the time that patients have access to medications, ranges from 0.44 to 0.83 in this patient population. The question remains: Can medication adherence be improved in patients with RA, which may in turn improve long-term outcomes?

A single-center, retrospective cohort study was conducted at an integrated health system specialty pharmacy (HHSP) at a major teaching medical center. The objective of this study was to evaluate adherence to specialty medications and to identify characteristics associated with adherence in patients with RA utilizing an integrated HSSP. Patients who filled prescriptions at the HSSP during July 1, 2016 and June 20, 2107 and who were receiving abatacept, adalimumab, certolizumab, etanercept, tocilizumab, or tofacitinib were included in the study.

To enhance patient-care coordination, a pharmacist and pharmacy technician were embedded in an outpatient clinic at the medical center. Patients were excluded from the study if the prescriber was not on staff at the healthcare system, if the provider had recommended a gap in treatment (e.g., during pregnancy, if infections lasted longer than 90 days, or if the patient was prescribed an extended drug holiday), if samples were provided that would last more than 3 months, or if the patient was receiving multiple overlapping specialty medication prescriptions.

The primary outcome of the study was medication adherence, which was measured by the proportion of days covered (PDC). PDC, which was calculated at the patient level, was determined by the number of days that the patient had medication available within the observation window divided by the length of the observation window. Medication availability was based on the number of days’ supply at each fill. Any excess medication from a previous refill was shifted forward.

A total of 675 patients receiving 753 prescriptions were included in the study. Study patient characteristics included a mean age of 55 years, 77% were female, 90% were Caucasian, 29% were treatment-naïve (i.e., had not filled a prescription for a specialty medication included in the study within 6 months prior to the study period), and 60% had commercial insurance.

The most frequently prescribed RA specialty drugs were etanercept (14.5%), adalimumab (14.1%), tofacitinib (12.4%), abatacept (11.7%), certolizumab pegol (4.9%), and tocilizumab (2.7%). Approximately three-quarters of the patients had received financial assistance. Despite the high cost of these medications, the median interquartile range for the average-out-pocket cost per fill was $1.50 (range: $0-$5). Patients filled their specialty medication a median of nine times (range: 6-12). The mean PDC was 0.89 and median PDC was 0.95 with 80% of patients achieving a PDC > 0.80, which is the minimum adherence threshold established for noninfused biologic medications used to treat RA patients. Higher PDC were associated with older age, male gender, and treatment naivety in both univariate and multivariate analyses.  

Government versus commercial insurance was associated with higher PDC rates in univariate analysis only. For every 10-year increase in age, there was 17% higher odds of patient adherence (odds ratio [OR] 1.17, CI, 1.04-1.32). Interestingly, men were 58% more likely than women to have greater adherence (OR 1.58, CI, 1.15-2.18). Treatment-naivety increased adherence by 4% (OR 1.04 CI, 2.21-4.18). There was a significant nonlinear association between the average out-of-pocket cost per fill, with higher adherence observed among patients with $0 cost per fill; higher adherence leveled off at $6 per fill.

A number of limitations were identified in this study, including that it was based on claims data and may not accurately reflect medication-taking behaviors or gaps in therapy; the study did not address primary nonadherence, which refers to when a medication is ordered but the prescription is not filled by the patient; the cross-sectional, retrospective nature of the study did not allow for the establishment of causality; and disease severity scores were not included.  

Nonetheless, this study demonstrated that it is possible to achieve high adherence rates and low patient out-of-pocket cost when an HSSP is utilized.  The investigators also delineated patient characteristics that are associated with adherence. Specialty pharmacists can use this information to target RA patients on noninfusable biological agents who are at risk for nonadherence. They can also help patients navigate the maze of reimbursement paperwork required for cost-sharing programs from the manufacturers of these biological agents.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

 « Click here to return to Specialty Pharmacy Update.