Medical experiments come under greater scrutiny than ordinary medical practice. There are good reasons for such precautions, but this leads to a sort of paradox. As Frederick Mosteller observed
We have a strange double standard now. As long as a physician treats a patient intending to cure, the treatment is admissible. When the object is to find out whether the treatment has value, the physician is immediately subject to many constraints.
If a physician has two treatment options, A and B, he can assign either treatment as long as he believes that one is best. But if he admits that he doesn’t know which is better and says he wants to treat some patients each way in order to get a better idea how they compare, then he has to propose a study and go through a long review processes.
I agree with Mosteller that we have a strange double standard, that a doctor is free to do what he wants as long as he doesn’t try to learn anything. On the other hand, review boards reduce the chances that patients will be asked to participate in ill-conceived experiments by looking for possible conflicts of interest, weaknesses in statistical design, etc. And such precautions are more necessary in experimental medicine than in more routine medicine. Still, there is more uncertainty in medicine than we may like to admit, and the line between “experimental” and “routine” can be fuzzy.