I take flecainide, beta blocker and an anti-coag. I also take a magnesium supplement (daily) and coenzyme Q10 (every second day).
I drink coffee occasionally - only when I need the caffeine - and have noticed recently that the coffee makes me feel like I have a seriously upset stomach (without needing the toilet!), but only sometimes.
Could this be an interaction with the Q10? Which would explain why i feel it only sometimes and not every time I drink coffee.