Introduction: Rheumatoid arthritis (RA) is a chronic autoimmune disease that is severely debilitating with a prevalence in the Philippines of 0.17-0.4%. This study aims to determine rate of methotrexate (MTX) toxicity, identify risk factors and comorbid conditions predisposing to toxicity and describe management of MTX toxicity.

Methods: Rheumatoid arthritis (RA) cases from the Rheumatoid Arthritis Database and Registry (RADAR) diagnosed by the 1987 ACR criteria receiving MTX monotherapy or combination disease modifying anti-rheumatic drugs (DMARDs), with at least one dose of treatment, were included. Patients were grouped into those with and without adverse events (AE). Disease activity was measured using DAS 28-ESR. Baseline characteristics, duration of use, dose, concomitant drugs and all toxicities were listed. Management of AEs were described. Independent t-test and Mann-Whitney U test were used for numerical data and Chi-square and Fisher’s exact test for continuous data.

Results: One hundred ninety four patients are included, with 95% females, age 35-64 years, disease duration of 0.2-10 years. Eighty three percent are on methotrexate monotherapy. Fifty cases (25.77%) all with dose of 8.75±2.5 had AEs: hepatotoxicity (52%), gastrointestinal (24%), hematologic (14%), dermatologic (8%), pulmonary (6%). Risk factors directly correlated with toxicity were older age (p=0.024), disease duration (p=0.024 ), dose (p<0.000), duration of use (p≤0.001), anemia (p=0.038) and osteoarthritis (p=0.011).Management included dose reduction (52%), dose retention with close monitoring (26%), addition of (24%) or shift to (22%) other DMARDS. Folate dose was increased in all cases.

Conclusion: Methotrexate (MTX) toxicity rate of RA patients from the RADAR is similar to those in literature. While dose reduction is the main management strategy, some patients’ doses were maintained while others were shifted to other DMARDS.

Keywords: rheumatoid arthritis, methrotrexate toxicity, rheumatoid arthritis database and registry

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