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Receptor theory is the application of receptor models to explain drug behavior. [1] Pharmacological receptor models preceded accurate knowledge of receptors by many years. [ 2 ] John Newport Langley and Paul Ehrlich introduced the concept that receptors can mediate drug action at the beginning of the 20th century.
In this context, the biological target is often referred to as a drug target. The most common drug targets of currently marketed drugs include: [4] [5] [6] proteins G protein-coupled receptors (target of 50% of drugs) [7] enzymes (especially protein kinases, proteases, esterases, and phosphatases) ion channels ligand-gated ion channels
When two drugs affect each other, it is a drug–drug interaction (DDI). The risk of a DDI increases with the number of drugs used. [1] A large share of elderly people regularly use five or more medications or supplements, with a significant risk of side-effects from drug–drug interactions. [2] Drug interactions can be of three kinds ...
Early forms of the receptor theory of pharmacology stated that a drug's effect is directly proportional to the number of receptors that are occupied. [14] Furthermore, a drug effect ceases as a drug-receptor complex dissociates. Ariëns & Stephenson introduced the terms "affinity" & "efficacy" to describe the action of ligands bound to receptors.
By knowing the interaction between a certain site of a drug and a receptor, other drugs can be formulated in a way that replicates this interaction, thus producing the same therapeutic effects. Indeed, this method is used to create new drugs. It can help identify which patients are most likely to respond to treatment.
Taking a more sophisticated approach, receptor reserve is an integrative measure of the response-inducing capacity of an agonist (in some receptor models it is termed intrinsic efficacy or intrinsic activity) and of the signal amplification capacity of the corresponding receptor (and its downstream signaling pathways).
The specificity of drugs cannot be talked about without mentioning the affinity of the drugs. The affinity is a measure of how tightly a drug binds to the receptor. If the drug does not bind well, then the action of the drug will be shorter and the chance of binding will also be less.
The Hill equation is useful for determining the degree of cooperativity of the ligand(s) binding to the enzyme or receptor. The Hill coefficient provides a way to quantify the degree of interaction between ligand binding sites. [5] The Hill equation (for response) is important in the construction of dose-response curves.