Background Methotrexate (MTX)-related gastrointestinal adverse effects are very common during MTX treatment in patients with juvenile idiopathic arthritis (1). JIA patients also develop adverse effects occurring before MTX intake and when thinking of MTX and behavioral complaints as conditioned responses to physical complaints experienced after MTX intake. Although MTX is the most commonly used anti-rheumatic in rheumatoid (RA) and psoaritic (PsA) arthritis as well, it is unknown whether the abovementioned MTX-related gastrointestinal adverse effects occur as frequently in adults.
Objectives To determine the prevalence of MTX-related gastrointestinal and behavioral adverse effects, termed MTX intolerance, in RA and PsA patients using the previously validated Methotrexate Intolerance Severity Score (MISS) (1)
Methods We performed a cross-sectional multicenter descriptive study in patients visiting three outpatient rheumatology clinics in The Netherlands. MTX intolerance was measured using the MISS, which assessed (i) adverse effects after MTX intake, (ii) adverse effects before MTX intake (“anticipatory”), (iii) adverse effects when thinking of MTX (“associative”) and (iv) behavioral adverse effects. These adverse effects included nausea, abdominal pain, vomiting and behavioural symptoms of restlessness, irritability and drug refusal. MTX intolerance was defined as ≥6 points on the MISS, with at least 1 point on anticipatory, associative or behavioral adverse effects.
Results Of the 170 consecutive patients, 66 patients (38.8%) reported adverse effects. According to the definition, MTX intolerance was found in 14 patients (8.2%). The prevalence of MTX intolerance was higher in patients using parenteral MTX than in patients using oral MTX (n=9 [27.2%] vs n=5 [3.6%]; p <0.001).
Conclusions Despite the fact 38.8% of patients reported adverse effects, only 8.2% of patients were intolerant to MTX according to the definition. This is remarkably less than the prevalence of MTX intolerance in JIA patients, which reached up to 50.5% (1). This was due to a significantly lower prevalence of both post-treatment and pre-treatment adverse effects in RA and PsA patients.
Bulatovic M, Heijstek MW, Verkaaik M, van Dijkhuizen EHP, Armbrust W, Hoppenreijs EP et al. High prevalence of methotrexate intolerance in juvenile idiopathic arthritis: development and validation of a methotrexate intolerance severity score. Arthritis Rheum 2011; 63(7):2007-2013.
Disclosure of Interest None Declared
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