Patterns of use, dosing, and economic impact of biologic agent use in patients with rheumatoid arthritis: a retrospective cohort study

BMC Musculoskelet Disord. 2004 Oct 14;5(1):36. doi: 10.1186/1471-2474-5-36.


Background: Variability in dosing and costs of biologics among patients with rheumatoid arthritis (RA) is of interest to healthcare descision-makers. We examined dosing and costs among RA patients newly treated with infliximab or etanercept under conditions of typical clinical practice.

Methods: Integrated pharmacy and medical claims data were obtained from 61 U.S. health plans. RA patients newly treated with infliximab or etanercept between July 1999-June 2002 were selected. A maintenance number of infliximab vials was determined after the "loading period" (2-3 infusions); those with >or= 2 occurrences of an increase in vials or an interval between infusions of <49 days were considered to have had escalated. For etanercept patients, escalation was based on >or= 2 instances of increased average daily dose. Multiple logistic regression analyses were conducted to assess variables associated with dose escalation. RA-related costs at one year post-initiation also were examined; comparisons were made using generalized linear models.

Results: A total of 1,548 patients were identified (n = 598 and 950 for infliximab and etanercept respectively). Infliximab recipients were somewhat older (50.5 vs. 46.6 years for etanercept). Nearly 60% of infliximab patients increased their dose at one year, compared to 18% for etanercept. Infliximab patients who escalated dose incurred a 25% increase in mean one-year costs (20,915 dollars vs. 16,713 dollars for no increase; p < 0.0001). Costs among etanercept patients did not substantially differ based on dose escalation (14,482 dollars vs. 13,866 dollars respectively).

Conclusions: Infliximab is associated with higher rates of dose escalation relative to etanercept, which contributes to substantially higher one-year medical costs.

MeSH terms

  • Antibodies, Monoclonal / economics
  • Antibodies, Monoclonal / therapeutic use*
  • Arthritis, Rheumatoid / drug therapy*
  • Drug Costs
  • Drug Utilization / statistics & numerical data
  • Etanercept
  • Humans
  • Immunoglobulin G / economics
  • Immunoglobulin G / therapeutic use*
  • Immunologic Factors / economics
  • Immunologic Factors / therapeutic use*
  • Infliximab
  • Middle Aged
  • Receptors, Tumor Necrosis Factor / therapeutic use*
  • United States


  • Antibodies, Monoclonal
  • Immunoglobulin G
  • Immunologic Factors
  • Receptors, Tumor Necrosis Factor
  • Infliximab
  • Etanercept