Background Infliximab is a chimeric monoclonal anti-TNF antibody developed to treat rheumatoid arthritis (RA) patients who have had a less than optimal response to previous therapy. It has been recommended that infliximab be given concomitantly with methotrexate (MTX) to prevent the development of autoantibodies.
Objectives To identify clinical response and adverse events in RA patients treated with infliximab for a period of 6 months, with a subgroup analysis of MTX-receiving (MTX-R) and non-receiving (MTX-NR) patients.
Methods RA patients receiving infliximab at our ambulatory infusion unit completed questionnaires regarding RA history, treatment, and measures of disease activity (HAQ) at baseline, and at 2 weeks, 8 weeks, and every 2 months thereafter. Patients were queried about side effects experienced between infusions. ANOVA statistics were used for comparison.
Results 36 patients were started on infliximab between January–July 2000 (F/M: 33/3, mean age: 63 + 12.9 y, mean disease duration: 15.3+10.2 y) and 24 patients completed 6 months of treatment. Patients had failed an average of 3 DMARDs prior to infliximab. HAQ scores for 24/36 patients who completed 6 months of treatment significantly improved from 1.95+0.60 to 1.21+0.67 (p = 0.0002). In subgroup analysis, the baseline characteristics of MTX-R and MTX-NR groups were similar with respect to age and disease duration. Twenty (56%) patients were not receiving MTX due to history of adverse event, allergic reaction or patient refusal. For patients who completed 6 months of infliximab: in MTX-R group, HAQ scores for 14/24 patients improved from 1.99+0.58 to 1.34+0.54 (p = 0.005); and in MTX-NR group HAQ scores for 10/24 patients improved from 1.89+0.65 to 1.05+0.81 (p = 0.02). During 6 months of follow-up, 3/10 (30%) of MTX-NR and 9/14 (64%) of MTX-R patients had a total of 23 adverse events after 198 infusions. There was no difference between the 2 subgroups with respect to the type of adverse events. Ten MTX-NR patients discontinued treatment before 6 months (adverse events: 7, inadequate response to treatment: 2, and non-compliance:1. Only 2 MTX-R patients discontinued treatment prior to 6 months, due to inadequate response.
Conclusion Following 6 months of infliximab treatment, RA patients with long-standing disease demonstrate a clinically important and statistically significant improvement in functional disability as measured by HAQ. However, our subgroup analysis suggests that infliximab administered without MTX carries a higher rate of discontinuation. These findings may be due to patient characteristics or our small sample size. Continuing follow-up of patients receiving infliximab in the absence of MTX will provide a better understanding of the true risk/benefit of infliximab used alone.
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