Can human resources ask me if I take prescription medication and if so what color my pills are ?

Specifically asked so what about Adderall ? A co worker went to HR and told them I get special treatment from my boss also stated we trade prescription medication all of this is untrue and there was absolutely no evidence of these allegations. HR asked several questions that made me uncomfortable like have I ever stayed the night with my boss, have I gone to lunch with my boss ,does my boss buy me energy drinks etc.I have literally broken down because my name is being slander, my work environment has become hostile in addition to this my car has been keyed .I have never spent time with my boss out side of work ever , we do have the same prescription but we do not "trade" "buy" or sale our medication . What should I do ?