Concepts in risk-benefit assessment. A simple merit analysis of a medicine?

The term 'benefit-risk ratio' is often used as a general term linked to the use of a medicine. To balance risk and benefit is, however, a very complex exercise. For most medicines the benefits are limited to a few indications and for an individual patient there is usually only a single benefit sought but the potential risks are multiple. Perceptions of risks versus benefits are influenced to a great extent by the context in which they occur. Thus, perception of risk may be different to actual risk. In the end in any given situation, the acceptable risk-to-benefit balance is an individual judgement on the part of the patient or the prescriber. For newer medicines, where there is likely to be limited experience, conservative estimates of the overall merit seem preferable so that the prescriber will use the drug critically. Subsequently, re-evaluation of the risk-to-benefit balance is necessary as greater knowledge of efficacy and adverse effects is acquired. It is possible to provide a general 'principle of threes' structure for a merit assessment based upon the concepts of seriousness, duration and incidence as related to disease indication, disease amelioration by a medicine, and the adverse effects ascribed to the medicine. This allows a rapid first comparison of medicines for a given indication. In using this general conceptual model in a transparent fashion for a given hypothesis and context, it is possible to identify the essential data used and assumptions involved that make up a merit statement. The quality and value, particularly of risk data, is problematic. Risk perception is an issue that needs to be clearly identified alongside a merit analysis. A simple merit assessment should pave the way for more focused studies.