• randomised controlled trials
• adverse events

We need to do a better job of keeping track of potential side effects when designing randomized clinical trials (RCTs). Consider an RCT for a new drug tested for the main or first order effect—the reduction of hypertension. Power calculations are carried out so that meaningful differences between the drug users and the controls can be detected on this effect. Second order effects—in this case, mortality—are those adverse events that are prospectively tracked, recorded, planned for in advance and, if sufficiently serious, may bring the trial to a halt through review conducted by a Data Safety Monitoring Board. Too rarely are there systematic prospective efforts to collect information on other unpredicted effects of the drug being tested. These third order effects may be important but are rare and unexpected and are not therefore necessarily sought out, so systematic data …