dose–response relationship

a principle relating the potency of a drug to the efficacy of that drug in affecting a target symptom or organ system. Potency refers to the amount of a drug necessary to produce the desired effect; efficacy refers to the drug’s ability to act at a target receptor or organ to produce the desired effect. Dose–response curves may be graded, suggesting a continuous relationship between dose and effect, or quantal, wherein the desired effect is an either–or phenomenon, such as prevention of arrhythmias. There is considerable variability among individuals in response to a given dose of a particular drug.