Reductions in Use of Colchicine after FDA Enforcement of Market Exclusivity in a Commercially Insured Population.

Abstract

A brand-name version of colchicine (Colcrys) was introduced after its manufacturer conducted a clinical trial in acute gout patients, leading to higher prices for this drug. We analyzed the impact of the new single-source colchicine product on prescribing and patient health spending as well as incidence rates of potentially dangerous concomitant use of clarithromycin and cyclosporine after formal FDA approval. We conducted a retrospective cohort study of UnitedHealth-affiliated enrollees newly diagnosed with gout or FMF. Among gout and FMF patients separately, we assessed linear trends in colchicine prescriptions, prescription drug costs, and total health care costs from 2009 to September 2010 (market exclusivity announced) compared to January 2011 (market exclusivity enforced) through 2012. Next, we estimated trends in co-prescription within 15days of clarithromycin, azithromycin (indicated on the Colcrys label for use in place of clarithromycin), and cyclosporine. Among gout patients, before Colcrys' market exclusivity, the odds of receiving colchicine within 30days of gout diagnosis increased 1.4%/month (OR: 1.014, 95% CI: 1.011-1.018). Following FDA action, the odds decreased by 0.5%/month (OR: 0.995, 95 % CI: 0.992-0.999) (p < 0.001). Similarly, among FMF patients, odds of initiating colchicine changed from an increase of 2.8%/month to a decrease by 7.6%/month (p = 0.01). Patients receiving colchicine experienced increases in average monthly prescription drug costs ($418 vs. $651, p < 0.001) and health care costs ($3,406 vs. $3,534, p < 0.001). Incidence rates of colchicine/clarithromycin co-prescription before and after FDA action did not change, while co-prescription of colchicine/cyclosporine increased after introduction of Colcrys [-0.75 monthly change in patients (95 % CI: -1.07, -0.43) vs. 0.13 (95 % CI: -0.16, 0.42), p < 0.001]. The FDA's actions were associated with a reduction in colchicine initiation and an increase in patient spending. By contrast, we did not observe any association with improvements in avoidance of potentially dangerous co-prescriptions.