Background/Purpose: Medication adherence and persistence have been demonstrated to have important implications for treatment effectiveness, cost, and safety. Methotrexate is one of the most commonly prescribed medications for the treatment of pediatric rheumatic diseases. Two injectable tumor necrosis factor alpha inhibitors (iTNFα), etanercept and adalimumab, are approved by the US Food and Drug Administration (FDA) for use in JIA, and recent data suggest that the prevalence of anti-TNFα medication use for JIA is now approaching that for adult rheumatoid arthritis. While JIA is the most common indication for these medications, they are also used in the treatment of additional rheumatic and inflammatory conditions. Despite their frequent use and established efficacy in clinical trials, few studies have examined children’s adherence and persistency with these medications.

The objective of this study was to measure adherence and persistence among children who were prescribed methotrexate and the injectable tumor necrosis factor alpha inhibitors (iTNFα) etanercept and adalimumab by an adult or pediatric rheumatologist.

Methods: Data were obtained from CVS Caremark^®, a large pharmacy benefits manager. Children were included if they were < 18 years of age, and had ≥ 1 prescription claim between January 2009 and December 2010 for methotrexate or an iTNFα that was prescribed by an adult or pediatric rheumatologist. The medication possession ratio (MPR) was calculated for each medication, with MPRs ≥ 80% indicating good adherence. MPRs were compared by route of administration, age, and by new users versus continuing users. Persistence was measured for new users of each medication from initiation until discontinuation, or for a maximum of one year.

Results: 1,964 children were included. The majority of children had MPRs < 80%. Children taking subcutaneous methotrexate had the lowest mean MPR (46.9%; median 44.9%; IQR 23%-69.6%) and the lowest persistence, with 26% of children continuing the medication at one year. Mean MPR was highest for iTNFα (65.7%; median 70.1%; IQR 46%-89.3%), as was persistence, with 52% of children continuing the medication at one year. Children receiving oral methotrexate had higher MPRs and persistence than those receiving subcutaneous methotrexate. Children < 13 years tended to have higher MPRs, but this was statistically significant only for oral methotrexate (61.1% versus 54.9%; p=0.02).

Conclusion: Adherence and persistence in this cohort varied by medication and route of administration. Both outcomes are important considerations for physicians prescribing these medications in routine clinical care and for the assessment of treatment effectiveness in the research setting.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/methotrexate-and-injectable-tumor-necrosis-factor-alpha-inhibitor-adherence-and-persistence-in-children-with-rheumatic-diseases/