Low dose of infliximab is inadequate in most patients with spondylarthropathies.

Objectives. The recommended starting dose for infliximab for ankylosing spondylitis 5mg/kg is higher than that for rheumatoid arthritis. Because of the high expense of the drug lower doses may be considered. We report our experience with lower initial doses. Methods. T h i rty patients with active SpA (16 psoriatic arthritis, 12 ankylos ing spondylitis and 2 undifferentiat ed) received 6 infliximab infusions. Pa tients had substantial axial disease (mean BASDAI at baseline 5.5). Concomitant therapy (methotrexate or pr e d nisolone) remained stable throughout treatment period. The mean initial dose of infliximab was 3.5 mg/kg/infusion. Clinical efficacy was assessed by BASDAI. The criterion for dose adjustment was a BASDAI improvement of less than 50%. The primary end-points were the proportion of patients requiring a dose adjustment and the percentage of patients achieving 50% improvement in BASDAI after 6 infusions. Results. In this cohort, 2 patients dis continued therapy, 1 for pulmonary infection and 1 for allergic re a c t i o n . Twelve patients (40%) showed 50% improvement in BASDAI between baseline and prior to the 7th infusion, while 15 patients (50%) had an improvement >2 points. To achieve clinical response the frequency and/or the dose of infliximab infusions were increased in 63% of patients. The mean infliximab dose increased from 3.5 mg/kg at the first infusion to 4.3 mg/kg (p<0.001) at the 7th infusion, resulting in a cumulative dose at the end of the study period comparable to the recommended one. C o n c l u s i o n s . In the majority of our SpA patients low starting doses of in fliximab re q u i red subsequent adjust ment. In these patients infliximab should be administered at the re c o m m e n d e d dose of 5mg/kg/infusion.