This document discusses drug interactions, which occur when one drug alters the effects of another drug. It defines different types of drug interactions including drug-drug, drug-food, drug-alcohol, drug-disease, and drug-laboratory interactions. It also describes pharmaceutical interactions that can be chemical or physical reactions between drugs. Pharmacological interactions are classified as pharmacodynamic or pharmacokinetic. Pharmacodynamic interactions directly influence drug effects, while pharmacokinetic interactions alter a drug's absorption, distribution, metabolism, or excretion. The document advises telling healthcare providers about all medications and supplements to avoid dangerous drug interactions.