OBJECTIVES: Pharmacovigilance is a very important tool for registration authorities and pharmaceutical industries to gather extra information on effectiveness and adverse effects of widely used drugs. Therefore, post-marketing research can lead to new insights on therapeutic usability and consequently changes in registration files or even result in market withdrawal. In September 2004, rofecoxib was withdrawn from the market for reasons of serious cardiovascular adverse events. Our objective was to evaluate trends in market-share and expenditures of cyclooxygenase-2 (cox-2) selective and non-selective NSAIDs around market withdrawal of rofecoxib. METHODS: Analyses were conducted using pharmacy prescription data from IADB.nl (50 pharmacies), covering a Dutch population of 500,000 subjects. NSAID-use was calculated per 10,000 of the population and presented quarterly from 2000-2006. Expenditures related to NSAID-use were calculated and presented in costs per 1000 of the population. RESULTS: After market introduction of cox-2 selective NSAIDs, proportional use increased to a maximum of 17% in the third quarter of 2004. After market withdrawal of rofecoxib, the number of subjects receiving celecoxib and etoricoxib increased enormously (from 22 to 48 and 18 to 28 subjects per 10,000 population, respectively), but decreased shortly thereafter. Similar results were found for new users. After market withdrawal, costs per 1000 population decreased with 65% and 24% for cox-2 selective and the total group of NSAIDs, respectively. During additional study follow-up, costs per DDD were generally increasing for cox-2 selective and decreasing for other NSAIDs. Further results will be presented on switching patterns from rofecoxib to other NSAIDs, with a specific focus on concomitant use of proton-pump-inhibitors for gastrointestinal protection and related extra costs. CONCLUSION: Withdrawal of rofecoxib from the Dutch market resulted in a decreasing number of subjects receiving cox-2 selective NSAIDs (class-effect) and lower expenditures for the whole group of NSAIDs. Further research is currently conducted to complete the full economic picture.