It's incumbent upon and actually a legal obligation for the physician to inform the patient of the potential for benefits and the potential for doing harm. That's the only way you can get informed consent. There are many legal opinions on this. Certainly, as a practising physician, I tell the patients what could happen, and I'm obligated to do it.
One of the problems that you allude to is the family's not knowing. In my practice, I try to bring the family into it, but there's a confidentiality problem here between the patient and me. The patient may not want the family to know, and then I'm obligated not to tell them. But I am totally obligated to tell the patients what they can expect from any procedure I do to them, including giving them a drug.