Medicines account for a substantial portion of healthcare spending, so they should be prescribed (and used) appropriately. One of the objectives of a national health service is to maximize the chances of achieving the desired effect, through medical and health interventions, while reducing waste of resources, so that the expected health benefits are likely enough to exceed potential negative outcomes. In this sense, appropriateness is a key aspect of healthcare quality, interacting dynamically with its other components: safety, effectiveness, equity, continuity of care, patient involvement, efficiency. Medicines are prescribed appropriately when clinical recommendations and, more generally, directions for their effective use (e.g. dose, duration, route of administration, interactions) are taken into account.
Pharmacoepidemiology is the branch of epidemiology that studies the effective and safe use of medicines in clinical practice, i.e. after their introduction into the market. The terms “pharmacovigilance” and “pharmacosurveillance” are sometimes used as synonyms for pharmacoepidemiology, but they actually refer to activities and methods used for assessing spontaneous reports of adverse drug reactions.