Adoption of new antiglaucoma drugs in finland: Impact of changes in copayment

Abstract Background: Copayments are common measures intended to control drug expenditures and promote rational prescribing. In Finland, new antiglaucoma drugs start with a high copayment, but once sufficient clinical experience is available, they are reevaluated and can receive a lower copayment status. Objective: This study assessed the effect of changes in copayment level on the adoption of 2 antiglaucoma drugs. Methods: A retrospective analysis was performed from 1997 to 2001 using the Finnish national register of reimbursed drug purchases, which covers ∼98% of all antiglaucoma drug purchases in the country. There were 172,293 purchases of dorzolamide (plain or combined with timolol) and 281,377 purchases of latanoprost. An interrupted time-series design from ∼30 months before and 20 months after the change in copayment was used in the analysis. The main outcome measures were the numbers of defined daily doses (DDDs) purchased and the monthly numbers of patients who purchased the study drugs for the first time before and after the change in copayment. Results: A substantial increase in consumption of both dorzolamide and latanoprost was seen immediately after the introduction of the lower copayment. The monthly consumption of dorzolamide was 60,713 DDDs higher and the monthly consumption of latanoprost was 49,330 DDDs higher than expected according to the utilization trend during the higher copayment period. Twelve months later, the observed consumption of dorzolamide was 109% higher and that of latanoprost was 21% higher than if the copayment had remained the same. The number of new patients using the study drugs peaked within 2 months of the lower copayment, but the amount consumed per patient per day remained quite stable. Conclusions: Decreasing the copayment of a new antiglaucoma drug to the same level as the copayments of alternative drugs accelerated the adoption of these new products in Finland.