Testing new interventions against placebo when effective treatments are already available is considered unethical [1] and dangerous for patients [2], so testing non-inferiority which aims at demonstrating that a new intervention is not unacceptably worse than standard clinical practice should be equally unethical [3,4]. The understanding is that part of the benefit can be given up in exchange for less important advantages – such as better tolerability, convenience, etc. – which are claimed though often not proved.
