Effectiveness of reducing infliximab dose interval in non-responder patients with refractory spondyloarthropathies. An open extension of a multicentre study.

OBJECTIVE To evaluate the therapeutic effectiveness of reducing the infliximab dose interval to 6 weeks in spondyloarthropathy patients not responding to 5 mg/kg every 8 weeks. METHODS After 30 weeks of infliximab therapy, 25 patients were classified as responders [Bath Ankylosing Spondylitis Activity Index (BASDAI) <4 cm or ESR <30 mm/h and CRP <5 mg/l, n = 15; group A] or non-responders (patients who did not achieve the response established for group A; n = 10; group B). Responders continued on 5 mg/kg every 8 weeks and non-responders decreased the dose interval to 6 weeks. BASDAI, Bath Ankylosing Spondylitis Functional Index (BASFI), ESR, CRP and ankylosing spondylitis assessment (ASAS) criteria were used to assess response. RESULTS At 62 weeks, 11 of 15 patients (73.3%, 95% confidence interval = 44.9-92.2%) from group A and three of 10 patients (30%, 95% confidence interval = 6.7-65.2) from group B were responders (P = 0.049). Eighty per cent (eight of 10 patients from group A) and 22.2% (two of 9 patients from group B) achieved 50% BASDAI improvement (P = 0.023), and nine of 11 patients (81.8%) and four of 10 (40%) from groups A and B, respectively, reached ASAS20 at 62 weeks (P = 0.08). CONCLUSION Patients on infliximab 5 mg/kg every 8 weeks with persistent disease activity may benefit from reducing the dose interval to 6 weeks.