"Oh, I'm on this new medication and I can't drink on it", may or may not be a useful fib for your beer festival. There's a surprisingly long list of medication where alcohol is contraindicated, including some common antihistamines.
It's what one of my friends did, said she couldn't drink because of medication and then "Oh, remember when I couldn't drink? When I could drink again, I decided that I didn't want to, so I've stopped."
congratulations!