Real-world data on MTX tolerance with regimens used in children versus adults

Objective: Methotrexate (MTX) is one of the most commonly used disease-modifying anti-rheumatic drugs which can cause gastrointestinal side effects. MTX intolerance is defined as gastrointestinal and behavioral symptoms occurring before and after MTX administration. This study aims to evaluate and compare the frequency of methotrexate intolerance in adult and pediatric patients.

Methods: Patients with a rheumatic disease who used oral or parenteral methotrexate for at least 3 months were included in the study. Methotrexate intolerance was assessed using the Methotrexate Intolerance Severity Score (MISS) questionnaire and visual analog scale (VAS). In the pediatric patient group, the MISS questionnaire and VAS assessment were applied to both patients and families.

Results: A total of 200 patients, 100 of whom were children, were enrolled in the study. The mean age for children and adults were 11.9 (± 3.7) and 52.0 (± 10.9). The prevalence of MTX intolerance was higher in the pediatric group, 64.0 and 10.0% (p < 0.001), respectively. Compared with oral administration, the patients receiving parenteral MTX had a higher proportion of MTX intolerance (p < 0.001). Younger age was the independent risk factor for MTX intolerance. There was a strong correlation between MISS and VAS scores between the evaluations of the patient and the family (p < 0.01, r = 0.95/p < 0.01, r = 0.94).

Conclusion: Methotrexate intolerance was higher in childhood. All patients using MTX should be monitored and questioned for signs of intolerance.