Rationale In Belgium, several policies regulating reimbursement of acid suppressant drugs and evidence-based recommendations for clinical practice were issued in a short period of time, creating a unique opportunity to observe their effect on prescribing. Aims and objectives To describe the evolution of prescriptions for acid suppressants and explore the interaction of policies and practice recommendations with prescribing patterns. Method Monthly claims-based data for proton pump inhibitors (PPIs) and H-2-antihistamines by general practitioners, internists and "astroenterologists were obtained from the Belgian (...) national health insurance database (1997-2005). The evolution of reimbursed defined daily doses and expenses after introduction of reimbursement regulations and dissemination of practice recommendations was explored. Results Recommendations had no impact on prescribing. All changes can be related to concomitant policies. Lifting reimbursement restrictions for cheaper products did not control growth or save costs in the Iona term. Only restricting reimbursement of all PPIs managed to curb the growth. We observed an unintended increase of non-omeprazole PPIs by gastroenterologists. Conclusions Reimbursement policies influence prescribing, but their effect can be unintended. A dialogue between policymakers and guideline developers, and evidence-based policies that are linked to clinical guidelines, could be an effective way to pursue both cost-containment and quality of care. (shrink)