1) Drug distribution involves the reversible transfer of drugs between the bloodstream and extracellular fluids and tissues through diffusion down a concentration gradient. 2) Many factors influence drug distribution, including physicochemical properties like molecular size and lipophilicity, tissue perfusion rates, and binding to proteins in blood and tissues. Small, uncharged, lipophilic drugs more readily penetrate tissues. 3) Understanding factors that affect drug distribution is important for predicting the onset, intensity, and duration of a drug's pharmacological effects in different parts of the body.