The doctor who gives you an experimental drug or unauthorized medical treatment is like the owner of a wild animal. Everyone knows that wild animals, like tigers or alligators, can be
dangerous and may attack if they get a chance, so they are not
allowed even one bite. The first time a wild animal attacks somebody, the owner is liable, because he should have expected it and taken precautions to protect the public. Any drug, treatment, or device that has not been approved by the Food and Drug Administration (FDA) is like a wild animal. The doctor does not have to know that you might react badly. He is exposing you to an unnecessary risk just by using it. If it injures you, he is liable.
What if you got an experimental or unauthorized drug from a friend, who brought it into the U.S. from another country? It is possible, but not very likely, that the government might prosecute her for practicing medicine without a license. But, you are out of luck. Since she did not hold herself out as a doctor, there was no doctor-patient relationship and no standard of care. You have only yourself to blame for taking professional advice and medicine from a layperson.
If a doctor is going to use a risky or experimental drug, an unauthorized medical treatment or device, he has to explain it carefully and have you sign a special consent form, which outlines all the risks and why it is necessary to take extra risks in your case. If the risks are not fully explained, and you do not consent with your eyes wide open and it harms you, you can sue in strict liability without having to show that the doctor did anything wrong, other than give you a drug, medical treatment, or device that was not approved as safe, or for a particular use, by the federal government.