What you eat and drink can affect the way your medicines work. Use this guide to alert you to possible "food-drug interactions" and to help you learn what you can do to prevent them. In this guide, a food-drug interaction is a change in how a medicine works caused by food, caffeine, or alcohol. A food-drug interaction can: prevent a medicine from working the way it should cause a side effect from a medicine to get worse or better cause a new side effect A medicine can also change the way your body uses a food. Any of these changes can be harmful. This guide covers interactions between some common prescription and over-the counter medicines and food, caffeine, and alcohol. These interactions come from medicine labels that FDA has approved. This guide uses the generic names of medicines, never brand names.