Objective: To determine the feasibility, safety, and potential clinical efficacy of intravenous (IV) doxycycline therapy for rheumatoid arthritis (RA), as well as its possible effects on serum and urinary markers of collagen breakdown.
Methods: The exploratory trial was designed as a 16-week, single-center, randomized, double-blind, placebo-controlled trial. Eligible subjects with active seropositive or erosive RA were randomly allocated into 3 treatment groups: doxycycline 200 mg IV, azithromycin 250 mg orally, or placebo. The blinded IV study drug was administered once daily for the first 3 weeks by home self-infusion and then weekly for the next 8 weeks, concurrent with the blinded oral study drug at the prescribed doses. The primary end points were the change between baseline and week 4 in the tender joint count, erythrocyte sedimentation rate, and urinary excretion of pyridinoline.
Results: The trial was stopped prematurely after enrollment of 31 patients. Three subjects were withdrawn because of worsening arthritis, and 1 patient was withdrawn when newly diagnosed with breast cancer. Infusion-related events occurred in 13 (42%) of 31 patients, but none were serious. There were 4 serious adverse events unrelated to the study drug, including a new diagnosis of breast cancer in 3 cases and hospitalization for abdominal pain in 1 case. No significant differences were observed across treatment groups in any of the 3 primary clinical end points.
Conclusion: Although IV doxycycline therapy was generally well-tolerated by patients in this trial, it did not show any evidence of reducing disease activity or collagen crosslink production.