It really depends on what types of drugs that other person is taking. You'd really have to know the history of what they took/take. Not to scare you at all, but there are people out there who shoot up, which could lead to STD's (HIV) and you'd certainly be at risk then. Not saying this person did/does that, but its something to consider. Many addicts won't tell you what they do and they do lie about it.
I guess we'd need to know more about what they take to give a better response.
Mark
I don't think so. even if you did it wouldn't be in high enough levels to register on a test.