In drug utilisation research, the primary purpose of intervention studies is to evaluate how changes in context affect drug use. The effect of an intervention can be assessed by comparing drug use within a population before and after its implementation or by comparing a population affected by the intervention to a control group that was not affected. In contrast to non-experimental studies-where data pertains to patients being treated in routine clinical care-experimental drug utilisation studies involve some degree of researcher involvement at the design stage. Cluster-randomised trial designs may be preferred over a traditional randomised controlled trial when the target of the intervention is a larger group of people rather than an individual. In drug utilisation research, quasi-experimental designs are used to evaluate the impact of educational and regulatory interventions to improve drug prescribing; and/or to assess the adherence to prescribing recommendations to maintain the positive benefit-risk profile of medicinal products.