Low-dose infliximab treatment for ankylosing spondylitis--clinically- and cost-effective

Infliximab has been shown to be effective in the treatment of ankylosing spondylitis (AS) when treated in a dose of 5 mg/kg at 6 weekly intervals. This dose of infliximab has not been determined by any structured randomized trials and has significant cost implications. We describe our experience of treating AS with low-dose infliximab (3mg/kg at 8 weekly intervals). The efficacy and cost implications are discussed.

Patients who had active AS [Bath AS Disease Activity Index (BASDAI) > or = 4] were treated with infliximab 3 mg/kg at 0, 2, 6 weeks and thereafter at 8 weekly intervals. Response to treatment was defined as 50% improvement in BASDAI. Other response criteria such as ASAS 20, 40 and five of the six criteria were also assessed. Direct drug costs for infliximab were determined.

Twenty-two consecutive AS patients received infliximab. All 22 completed treatment for 3 months, 15 patients for 6 months and 14 for 12 months. Mean age was 45 years (range 21-62) and mean disease duration 14.5 years (range 2-43). Of the patients, 54% achieved a 50% BASDAI response at 3 months and the benefit was sustained at 12 months in 63%. Similar response rate was seen with the other assessment criteria. Direct drug costs were significantly lower when low-dose infliximab regimen was used.

Low-dose infliximab (3 mg/kg at 8 weekly infusions) is effective in the treatment of AS. Higher doses are required in a small proportion of patients when treatment is only partially effective. Titrating the dose and frequency of infusions may be required in individual patients to achieve optimal response. Using low-dose infliximab has significant economic implications.