While I am horrified at the casual use of over-the-counter medications in America, I DO suggest that you bring along a few things you usually count on, whatever that might be! Tylenol, Immodium, whatever.
In Europe you have to buy these things in an Apotheke, they are NOT available in a supermarkt or drug store, and Europeans have a different approach altogether to medication, they will often recommend hot-water bottles and tea instead of drugs, in matter of fact, they have a rather deep mistrust of chemically based medications. Charming and wonderful, but maybe not good when you need something in the middle of the night in a foreign country!
I have had many American friends visit, and based on a few experiences, this is what I recommend them to do as well!