Pharmacodynamics: Ligand Concentration, Binding, and Effect

This lecture explores the relationship between ligand concentration, binding, and effect, focusing on allosteric modulators that bind to a separate site on the receptor, affecting agonist affinity and efficacy. It covers the effects of affinity- and efficacy-modifying allosteric modulators on the concentration-effect curve of an agonist. The lecture delves into the types of pharmacological antagonists, competitive and non-competitive inhibition, and the quantification of antagonism by IC50. It also discusses the action of agonists, inverse agonists, and competitive antagonists in terms of receptor states and binding sites. Furthermore, it examines desensitization, tachyphylaxis, and variability in drug response, including the therapeutic index and PK/PD modeling.