OBJECTIVES: Containing pharmaceutical budgets has encouraged generic prescribing policies. Across Europe, many patients have been switched from atorvastatin to generic statins, particularly simvastatin, but often at lower therapeutic doses. This study sought to estimate the potential clinical and economic effect if policy-induced switching to first generation statins occurred in Belgium as per previously observed patterns. METHODS: A Markov micro-simulation model was populated with 80 primary prevention Belgian patients from a 2007 observational study. Risks of first-onset cardiovascular disease (CVD) were estimated using a calibrated Framingham risk equation. With a baseline of January 2010, follow-up was simulated for 20 years. Decision analysis estimated the marginal effects of switching all patients from atorvastatin (weighted average daily dose [WADD] 20.7 mg) to simvastatin (WADD 31.6mg). Dose-specific, lipid-modifying effects of the two statins, CVD costs and utilities were sourced from published data. Annual discount rates of 3% and 1.5% were applied to costs and health effects, respectively. RESULTS: Of the 80 subjects on atorvastatin, 23 (28.9%) were predicted to develop CVD over 20 years. In the switched-to-simvastatin group, the predicted number was 26 (32.0%), equating to a ‘number needed to harm’ of 32. Switching was estimated to lead to a net cost saving of €581 per subject, but also a loss of 0.04 QALYs. These equated to an ICER of €13,608 per QALY gained (atorvastatin vs simvastatin). Sensitivity analyses indicated the results to be robust. CONCLUSIONS: Our preliminary analyses indicate that there would be an increase in the burden of CVD if Belgian patients are switched from atorvastatin to generic simvastatin at non-equipotent doses, as has happened in neighbouring countries like The Netherlands. This study highlights the need to consider the potential health and health economic impact of population-based switching policies.