Countermeasures against methotrexate intolerance in juvenile idiopathic arthritis instituted by parents show no effect.

Objectives: A high proportion of children with JIA will develop intolerance to MTX with anticipatory and associative gastrointestinal adverse effects. Parents and physicians frequently try to alleviate these symptoms with a variety of countermeasures. The objective of this study was to investigate the course of MTX intolerance within a 6 month period, and the effects of countermeasures on MTX intolerance severity.

Methods: We performed a prospective study of 196 consecutive JIA patients treated with MTX. Intolerance was determined using the Methotrexate Intolerance Severity Score (MISS) questionnaire. MISS and countermeasures instituted by parents or physicians were determined at four time points, each 2 months apart. Countermeasures, classified into four types (antiemetic drugs, covert dosing, taste masking and complementary medicine), were analysed using non-parametric statistics and mixed linear modelling, adjusted by propensity scoring for use of countermeasures.

Results: Ninety patients (46%) showed MTX intolerance, with 58 (64%) using countermeasures at time of inclusion. Median MISS at inclusion was 11 (interquartile range = 8.0-14.25), and did not change significantly over time. No significant difference in MISS score was observed between patients receiving countermeasures and those who did not. For specific countermeasures, MISS did not change significantly after introduction. Sensitivity analysis adjusting for propensity score indicated no significant association of MISS severity on parents' decision to implement any countermeasures.

Conclusion: MTX intolerance was present in many children with JIA and symptoms decreased little in the short term. Various modalities used as countermeasures against nausea by parents showed no discernible effect.