I admit to using the line, I'm on medication that doesn't interact with Alcohol right now. Most people are not so insensitive as to ask what. If they do, I say it is an antibiotic or something equally benign. It's kind of try, Alcohol is a drug your system doesn't need right now. No one else needs to know unless you want them to. I think back to my teen years when someone offered me drugs, and I got by with No thanks. Have a glass with water or soda handy, it also helps cut down on offers.