Methotrexate and injectable tumor necrosis factor-α inhibitor adherence and persistence in children with rheumatic diseases.

OBJECTIVE: To measure adherence and persistence with methotrexate (MTX) and injectable tumor necrosis factor-α (iTNF-α) inhibitors (etanercept, adalimumab) among children prescribed these medications by a rheumatologist. METHODS: Data were obtained from a US pharmacy benefits management firm. Children were included if they were < 18 years of age, had ≥ 1 prescription claim between January 2009 and December 2010 for MTX or an iTNF-α inhibitor that was prescribed by an adult or pediatric rheumatologist. The medication possession ratio (MPR) was calculated for each medication, with MPR ≥ 80% indicating good adherence. MPR 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 1 year. RESULTS: A total of 1964 children were included. The majority of children had MPR < 80%. Children taking subcutaneous MTX had the lowest mean MPR [46.9%; median 44.9%; interquartile range (IQR) 23%-69.6%] and the lowest persistence, with 26% of children continuing the medication at 1 year. Mean MPR was highest for iTNF-α (65.7%; median 70.1%; IQR 46%-89.3%), as was persistence, with 52% of children continuing the medication at 1 year. Children age < 13 years tended to have higher MPR, but this was statistically significant only for oral MTX (61.1% vs 54.9% in children age ≥ 13 yrs; 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.