Talk to the person. Ask them simple questions like what their name is, where they live, how is work or school. Remind them that everything they are feeling is caused from a drug and it WILL wear off. Tell them that everything is okay with you, and that the real world is fine. Ask them if they want to be held or if they want space. If they don't want to talk, don't make them talk. Just remain calm, everything is alright.