Pharmacology is the branch of medicine and
biology concerned with the study of
drug action
, where a drug can be broadly defined as any man-made, natural, or endogenous molecule which exerts a biochemical and/or physiological effect on the cell, tissue, organ, or organism. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function. If substances have
medicinal properties, they are considered
pharmaceuticals. The field encompasses
drug composition and properties,
interactions,
toxicology, therapy, and medical applications and antipathogenic capabilities. The two main areas of pharmacology are
pharmacodynamics and
pharmacokinetics. The former studies the effects of the drugs on biological systems, and the latter the effects of biological systems on the drugs. In broad terms,
pharmacodynamics discusses the interactions of chemicals with biological
receptors, and
pharmacokinetics discusses the absorption, distribution, metabolism, and excretion of chemicals from the biological systems. Pharmacology is not synonymous with
pharmacy and the two terms are frequently confused. Pharmacology, a biomedical science, deals with how drugs interact within biological systems to affect function. It is the study of drugs, of the reactions of the body and drug on each other, the sources of drugs, their nature, and their properties. In contrast,
pharmacy, a health services profession, is concerned with application of the principles learned from pharmacology in its clinical settings; whether it be in a dispensing or clinical care role. In either field, the primary contrast between the two are their distinctions between direct-patient care, for pharmacy practice, and the science-oriented research field, driven by pharmacology.