In addition to lambada's response about the doctor-patient relationship, there is also an expectation of common knowledge. You are not expected to know anything about the medicine given to you since that is the doctor's responsibility, but you are expected to take it as instructed. You are expected to know that if you do anything unusual with it you may be putting yourself in danger.

If you do something idiotic like crush it up into powder, then snort it at five times the dosage, that's on you. If you then go into shock and suffer a stroke, guess what.... zero dollars, stop wasting the court's time, you are an idiot.