What legal drugs can numb pain or numb pain and knock you out?

Short answer - there aren't any legal drugs that will do what you asking. There are things that can disturb the pain sequence, and are legal. They are problem specific. There are a lot of these but I do need to know what type of pain you are talking about. Physical or mental, joint or muscle, surface or internal. There are little or no side effects and can be used for life without developing any dependency.pp