Pharmacology is a branch of medicine and pharmaceutical sciences which is concerned with the study of a drug or medication action. The two main areas of pharmacology are pharmacokinetics and pharmacodynamics. Pharmacokinetics studies the effects of biological systems on a drug, pharmacodynamics studies the effects of a drug on biological systems. In broad terms, pharmacokinetics discusses the absorption, distribution, metabolism, and excretion (ADME) of chemicals from the biological systems and pharmacodynamics discusses the chemicals with biological receptors.