The likelihood of receiving the drug determines the size of the placebo response in IBS trials

While placebo controlled trials are common in the evaluation of novel drugs, they have been questioned because of the ethical problems of withholding effective treatment in (pain) patients. As alternative, comparator controlled trials ave been proposed. Both however, differ in the likelihood of providing effective treatment: 50% and 100%, resp. Methods: We investigated whether the likelihood of receiving drug or placebo determines the size of the drug response and the size of the placebo response (DR, PR) in treatment studies of irritable bowel syndrome (IBS). Results: In 92 published randomized placebo-controll…