Retrospective analysis of utilization patterns and cost implications of coxibs among seniors in Quebec, Canada: what is the potential impact of the withdrawal of rofecoxib?

Objective: In September 2004, the manufacturer of rofecoxib announced a voluntary worldwide withdrawal of the drug. The impact of this withdrawal on drug budgets is unclear. This study evaluated average daily doses and costs of rofecoxib and celecoxib and concomitant use of gastroprotective agents (GPAs) in elderly patients with osteoarthritis (OA) or rheumatoid arthritis (RA) in Quebec, prior to the rofecoxib withdrawal.

Methods: This retrospective cohort study used prescription drug and medical service data from the Quebec government health agency administrative database and included coxib users > or =66 years of age with OA or RA who filled > or =3 consecutive rofecoxib or celecoxib prescriptions in 2001-2002. Results were adjusted for gastrointestinal risk factors and other patient baseline characteristics.

Results: Data were analyzed for 11,975 rofecoxib and 12,480 celecoxib users. Mean daily dosages were 20.7 mg for rofecoxib and 231.3 mg for celecoxib. Rofecoxib users consumed a mean +/- SD of 0.95 +/- 0.43 pills per day, and celecoxib users took 1.34 +/- 0.65 pills per day. Mean +/- SD unadjusted daily acquisition costs were $1.18 +/- $0.53 (Canadian) for rofecoxib and $1.45 +/- $0.74 for celecoxib. After adjusting for patient baseline characteristics, the mean daily acquisition cost for rofecoxib was $0.25 lower than for celecoxib. Rofecoxib users were less likely than celecoxib users to fill a GPA coprescription (odds ratio 0.88; 95% confidence interval 0.81, 0.95). Subgroup analyses yielded comparable results.

Conclusion: Celecoxib appears to be a more expensive therapeutic option than rofecoxib due to a relatively higher daily dose and tablet consumption.