Pharmacology focuses on substances that alter the body's functions, not create new ones. Drugs can only amplify, negate, or block existing bodily functions, maintaining homeostasis. The distinction between a drug and medicine lies in the therapeutic intention; medicine is designed to treat a disease, while a drug simply alters physiology. Medicines aim to create a specific change at the gene level, unlike drugs that manipulate genes or allow the body to express them differently. Interventions like CRISPR, which change genetic codes, may not fit the definition of a drug due to their ability to modify genes beyond the body's normal capacities.