Children with juvenile idiopathic arthritis frequently experience interruptions to their medical therapy.

Aim: To study real-life experiences of drug treatment discontinuations and safety in a well-defined cohort of patients with juvenile idiopathic arthritis (JIA), over an eleven-year period in Uppsala County, Sweden.

Methods: Clinical charts of all incident and prevalent cases of juvenile arthritis were reviewed prospectively by an experienced paediatric rheumatologist. Each patient file was supplemented retrospectively regarding hereditary diseases, clinical data and aspects of pharmacological treatment.

Results: Severe adverse events from methotrexate or biological agents were rare, but 84 occasions of interrupted therapy due to adverse events or inefficacy were identified within 225 treatment periods (37.3%) in the 156 patients (108 girls and 48 boys) studied. The median observation period was 8.6 years after disease onset (minimum 1.33, maximum 17.5 years). Oral and subcutaneous methotrexate caused adverse events in 22.6% of the treatment periods and biological agents in 19.2% (p = 0.71). Discontinuation of treatment periods was equally common for methotrexate (38.7%) and biological agents (33.3%) (p = 0.53).

Conclusion: Our study shows a high percentage of interrupted medical therapies, due to adverse events or inefficacy, in children with JIA. Adverse events from methotrexate and biological agents were seldom severe. The results highlight the need for better predictive factors to guide therapy.