In medical science, as in all walks of life, we are impressed by dramatic effects. If a new treatment seems much better than an old one initially, there is often impatience to get on and use it, and people question why one would want to conduct formal trials.
Doctors who feel this enthusiasm for what they see as a breakthrough often argue that it’s not ethical to do a randomised trial of an exciting new treatment, because the benefits seem so obvious, and randomisation means that half the patients are deprived of them. Of course breakthroughs sometimes turn out to be false dawns, but the idea that something might be so obviously better than what we have now that it doesn’t need a randomised trial is pretty widespread in medicine.
Read more (Oxford Science Blog)