Pharmaceutical Chemistry is the branch of Pharmacy that deals with the study of the chemistry of drugs. A drug is defined as a compound taken by humans (and by extension, other forms of life) for therapeutic purposes, either literally for treatment or for preventive reasons. The drug, upon introduction into the organism, undergoes various, often complex and multi-level processes that involve its action, metabolic modification, and ultimately its elimination. The significant development of Biology has provided us with important knowledge about the functions of life at the cellular and molecular level, and this knowledge, combined with the information from Medicine, has made it possible in many cases to understand the mode of action of drugs. The purpose of Pharmaceutical Chemistry is precisely to exploit the information from Biology and Medicine, with the collaboration of knowledge from informatics, chemistry, physics, and mathematics, in order to enable the exhaustive study of the drug's effect on the organism.