Infliximab dose and clinical status: results of 2 studies in 1642 patients with rheumatoid arthritis.

OBJECTIVE: Infliximab is an effective anti-tumor necrosis factor (TNF) agent widely used in the treatment of rheumatoid arthritis (RA). Initially recommended at a dose of 3 mg/kg, subsequent label revisions allowed doses up to 10 mg/kg or at 4-week intervals rather than the originally suggested 8-week intervals, if clinically indicated. The doses used have implications for efficacy and costs, but no data exist for actual dose used in the US. This study evaluates the dosage and rates of increase in infliximab-treated patients with RA.
METHODS: Study 1: Review of patient charts and infusion records for 394 RA patients from 2 large rheumatology practices comprising 15 rheumatologists in Dallas, Texas. Study 2: Survey of 1324 RA patients using infliximab participating in a longitudinal study of RA outcomes. Patients completed a detailed questionnaire about clinical status and infliximab use.
RESULTS: The results of the 2 studies were similar: the average infliximab dose was 5 mg/kg, increasing most rapidly until the end of the first years, after which the increase was slowed. Increases > 3 mg/kg occurred in 61% of patients in Study 1 and 56% in Study 2. The 8-week treatment interval was almost universally used, and more than 95% of infusions occurred in this interval. The most common reason for increase in dose was insufficient response. Among patients who completed 4 infusions, 75% remained on therapy at 2 years after infliximab start. The average improvement in Health Assessment Questionnaire disability score was 0.28.
CONCLUSION: Infliximab dose increases are common, particularly during the first year of treatment. The average dose is 5 mg/kg. Seventy-five percent of patients continue using infliximab 2 years after treatment onset.