As prescribers, we all aspire towards the goal of providing safe and effective medicines for our patients. At the bedside, we are routinely confronted with the challenge of determining which treatment (if any) offers the most appropriate tradeoff between benefit and harm. In ideal circumstances, we would base this assessment on the findings of a systematic review. But the reality is that systematic reviews and randomised controlled trials tend to focus on efficacy and seldom pay much attention to adverse effects.1 2 In contrast, product datasheets and drug reference texts (such as the British National Formulary) are laden with comprehensive lists of adverse effects. Is there really any need to look beyond these ubiquitous, easily accessible sources of safety data?

However, all is not what it seems. Lists of adverse effects can be extremely lengthy—for example, Bracchi noted 54 adverse effects for fluoxetine—and incorporating them into a useful analysis of the benefit:harm balance seems impossible.3 More recently, a member of the British public wrote to the national press …