Agonists bind to and activate receptors, forming drug–receptor complexes that initiate various biochemical processes at the cellular level, leading to a pharmacologic response. The magnitude of this response is directly proportional to the fraction of activated receptors, which depends on the drug concentration and receptor sensitivity. As the administered dose increases, the drug concentration at the receptor site also increases, resulting in a stronger biological response. The graded dose–response curve illustrates the relationship between response and drug concentration, with the magnitude of the response gradually increasing as the drug dose increases. The maximum effect is observed once the receptors are fully saturated. When plotted semi-logarithmically, the hyperbolic curve becomes sigmoidal, describing drug potency and efficacy. The EC50 value determines the drug's potency, while the Emax value determines efficacy.