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Not if they agreed to be part of a study. Otherwise, no one could use a placebo.

As part of a study? No. This is how studies are done. Give one set of people the real medicine and another people the fake one and see what happens. They are told before hand that they could receive the fake medicine/treatment and they must agree to the study.

In a study, patients aren't lied to exactly; they're told their either going to receive a real treatment or a phony one, but they won't know which.