The effects of coxib formulary restrictions on analgesic use and cost: regional evidence from Canada.

Background: Public insurance plans for pharmaceuticals in Canada differ substantially across provinces in the conditions under which pharmaceuticals are reimbursed. Coxibs provide a good example. Québec had no restrictions on reimbursement for these drugs. Ontario required physicians to submit the clinical indications for their use on the prescription. British Columbia required physicians to seek and receive prior authorisation from the drug plan.

Objective: This study compares the effects of different reimbursement policies on coxib, non-selective non-steroidal anti-inflammatory drugs (nsNSAIDs), and gastro-protective agent (GPA) use and cost.

Study Design: Analysis of retrospective time series analysis of all NSAID and GPA administrative claims data from April 1997 through December 2002.

Setting: Administrative claims data from April 1997 through December 2002 for each of the publicly funded drug plans in Québec, Ontario, and British Columbia. In addition, we obtained data from BC PharmaNet, which records all dispensed prescriptions in British Columbia.

Patients Or Other Participants: Senior beneficiaries (>or= 65 years).

Main Outcome Measure: We compared the projected total NSAID utilisation in the absence of coxib reimbursement restriction with actual utilisation by province and drug category. Projected utilisation was based on ARIMA modelling and reported as the number of defined daily doses (DDDs) per 100 senior (>or=65 years) beneficiaries/month.

Results: In Ontario, under its "limited use" policy, uptake and steady-state use of coxibs was similar to that in Québec, where there were no restrictions. In British Columbia, publicly funded use of coxibs was 6% of that in Ontario and Québec. Despite a shift to private reimbursement, total coxib use in BC was only 50% of use in Ontario and Québec. The use of all NSAIDS (nsNSAIDS plus coxibs) increased for all provincial drug plans except for BC. The increase and overall rate of total NSAID use was greatest in Ontario. Neither Ontario's nor BC's policies had an impact on use of nsNSAIDs or GPAs.

Conclusion: Only BC's policy effectively limited publicly funded coxib use. However, there was substantial cost-shifting to out-of-pocket and third party insurance plans in BC.