A POA only gives you the same rights that your mother would have herself if she were in the position to make decisions about her own health care.  Apparently, even if they had a patient who had her wits about her and said I do not want to take that anymore, they would still bring it to her until the doctor said to stop.  It is a stupid rule, but at least if a person does not want to take medicine, the person can simply not swallow it.  You can not do that for your mother.  But a POA does not give you any more rights to dictate care than your mother would have herself if she were in her right mind.