Serenity. I can certainly relate although in my 3 weeks of being sober I have not been put in that type of situation. Quite frankly I dread the time when I have to be. I have been asked to have a glass of wine because that was the thing we used to do. I used the same excuse as you- I didn't want to drink because I started taking blood pressure medication.
This will be the excuse I use but I worry about upcoming events, family gatherings, weddings, etc. where people are accustomed to me having wine. I keep trying to tell myself to cross that bridge when I come to it.
I think your boss and anyone else will understand about the medical aspect of not drinking. Good luck to you!