Medicine costs are difficult to predict. Budget impact estimates for extramural medicines compared with actual expenditures Kosten van geneesmiddelen zijn moeilijk te voorspellen: Kostenconsequentieramingen voor extramurale geneesmiddelen vergeleken met gerealiseerde kosten

Objective: To study the correspondence of budget impact analyses with the actual expenditures. The advice of the Dutch Health Insurance Board (CVZ) on the inclusion of medicines in the reimbursement system entails an estimation of the budget impact. Design: The estimated total costs for new medicines were compared to the actual expenditure three years after inclusion in the reimbursement system. Methods: For a selection of 18 new medicines the estimated total costs were identified based on the cost estimations of CVZ published in the period 1999-2003. Information on the expenditure on these medicines was obtained from the Foundation of Pharmaceutical Statistics (SFK) and the Dutch Drug Information System (GIP). Results: The estimated budget impacts of the selected medicines vary from € 0.05 million to € 30 million each year. A consistent method for cost estimation is lacking and a criterion for acceptable accuracy of the cost estimation does not exist. The data on both cost estimates and actual expenditures present a considerable uncertainty. For half of the selected medicines the cost estimates were higher than the actual expenditures and for half the estimates were lower than the actual expenditures. The deviation of the cost estimate with actual expenditure ranged from 1% to 1132%. Conclusion: Budget impact analyses on extramural medicines only give an indication of the order of magnitude of the budget impact. The use of the cost estimates in the decision on the uptake in the reimbursement system could therefore be questioned seriously.