Читать книгу Fundamentals of Pharmacology for Paramedics - Группа авторов - Страница 26

With only one or two exceptions (such as drugs which absorb other substances, e.g. charcoal or resins), drugs act by binding chemically to specific binding sites. It is this fact which explains the various observed characteristics of a drug, for example, the relationship between the shape of a drug molecule and its actions; the relationship between how readily it binds to its site of action and the concentration of drug needed at the site of action to bring about a therapeutic effect; the relationship between the number of different binding sites the drug can bind to and the number of different effects it produces; the strength with which it binds to the site and length of time for which it exerts its effects, and so on.

The site at which a drug binds to have its effects is known as the receptor for that drug, and it may be a receptor normally used by endogenous signalling molecules, such as hormones or neurotransmitters, or a binding site on an enzyme, ion channel or transport molecule. A substance binding at any of these sites would be able to alter physiological function when the structure to which the drug is binding is itself responsible for producing various physiological changes.