It should be noted that one of the components to many drug and observational trials is the ability to halt the trial and switch patients on or off drugs as it b

It should be noted that one of the components to many drug and observational trials is the ability to halt the trial and switch patients on or off drugs as it becomes clear that one treatment is vastly superior. The original studies of aspirin and heart disease were, for example, halted because the benefits were so clear that it wasn't considered ethical to keep the placebo arm untreated. Several HIV trials have similarly been halted because the treatment was showing no or negative effects.