Objective The provision of medicines through state public hospitals is comparatively restrictive compared with the federally funded Pharmaceutical Benefits Scheme (PBS). Individual states are progressively moving towards statewide medicines formularies. Although a statewide formulary has existed in Queensland for some time. The effects of hospital formularies on medicines utilisation and policy in Australia has not been quantified. Thus, the aim of the present study was to quantify the effects of the Queensland Health List of Approved Medicines (LAM) on medicines utilisation in Queensland at a state and PBS-purchasing level and describe the implications for medicines policy. Methods This study used a quasi-experimental design with an interrupted time series (with control for PBS) examining utilisation effects of medicines within the therapeutic classes of proton pump inhibitors and non-vitamin K oral anticoagulants with LAM listing or delisting. Results The LAM was demonstrated to be highly effective at controlling utilisation within Queensland Health purchasing. Effects on PBS utilisation were evident, resulting in increases in generic utilisation (where available) and associated reduced total costs both within Queensland Health and to the PBS. The full benefit is likely underestimated due to limitations in the PBS datasets. Conclusion The LAM is a highly effective state medicines policy tool with demonstrable effects on PBS utilisation. With increased use of statewide medicines formularies, this will be an increasingly relevant aspect of Australia's overall medicines policy. What is known about the topic? State medicines policy is comparatively restrictive compared with the federal PBS. Most Australian states have, or are developing, statewide medicines formularies. What does this paper add? By examining several classes of medicines, a substantial quantitative effect of the Queensland state formulary on both state and PBS medicines utilisation can be demonstrated. Increased use of generic medicines and reduced costs are seen. What are the implications for practitioners? With increased use of state medicines formularies, state medicines formularies will become increasingly relevant to medicines policy makers and advocates at both the state and federal level.