The influence of previous and concomitant leflunomide on the efficacy and safety of infliximab therapy in patients with rheumatoid arthritis; a longitudinal observational study.

OBJECTIVE To investigate the influence of previous and concomitant leflunomide on the efficacy and safety of infliximab therapy in rheumatoid arthritis (RA) and to compare it to infliximab in combination with other disease-modifying anti-rheumatic drugs. METHODS RA patients starting infliximab therapy were prospectively followed from January 2000. Every 3 months data were collected regarding disease activity (DAS28), adverse events and treatment changes. In the primary analyses all patients were classified into a leflunomide group (LEF group) if they had used leflunomide during infliximab therapy or within 6 months prior to starting infliximab therapy, the latter because of the long half-life of leflunomide. All other patients were considered as controls (non-LEF group). Secondary drug survival analyses were performed with the LEF group consisting only of patients on active leflunomide at the start of infliximab (active LEF group). RESULTS A total of 162 RA patients started infliximab therapy (57 in the LEF group, 105 in the non-LEF group). No statistically significant differences in baseline characteristics were observed between the groups. Maximum follow-up time was 46 months for both groups. No differences in drug survival, disease activity or adverse events were observed between the groups. In both groups an increase in patients positive for antinuclear antibodies (ANA) was seen. ANA positivity at start did not predict DAS28 or the occurrence of adverse events. Secondary drug survival analyses showed no differences between the active LEF group and the non-LEF group. CONCLUSION The results indicate that the administration of infliximab after or simultaneously with leflunomide is safe and efficacious in RA patients.