I am not a medical professional and cannot give you any medical advice.
With that said, there is no money in DE for drug companies so the research is not great.
I have found nothing to indicate any contraindications. DE works mechanically scraping the gut so there is no chemical reaction side as with drugs does not exist.
My consideration (and only a guess) is that DE and CB are very mineral rich. The body absorbs the beneficial minerals from them in a similar way that the body absorbs nutrients from food. So if the directions for a medicine say not to take it with food, I would avoid taking DE and CB with the medicine.
We recommend taking DE/CB on an empty stomach for maximum benefit.
One other note - start any cleanse slowly. Any detoxing can cause headaches, upset stomach, etc. I personally experienced this when I started taking DE/CB for about the first 2 days. I now take DE/CB at night on an empty stomach right before I go to bed.