Pharmacology: The study of drugs, their sources, their nature, and their properties. Pharmacology is the study of the body's reaction to drugs. It emerged as a major area in American medicine largely due to the efforts of John Jacob Abel (1857- 1938) who stressed the importance of chemistry in medicine, did research on the endocrine glands, first isolated epinephrine (adrenaline), crystallized insulin (1926), and became the first pharmacology professor in the U.S.