General Pharmacology-part 4-Dose response curve

1. Efficacy: Efficacy is the magnitude of response caused by a drug when it interacts with a receptor. Efficacy is dependent on the number of drug–receptor complexes formed and the intrinsic activity of the drug (its ability to activate the receptor and cause a cellular response). Maximal efficacy of a drug (E max) assumes that all receptors are occupied by the drug, and no increase in response is observed if a higher concentration of drug is given. 2. Potency: Potency is a measure of the amount of drug necessary to produce an effect of a given magnitude. The concentration of drug producing 50% of the maximum effect (EC50) is usually used to determine potency. 3.Therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response. Therapeutic index is a measure of drug safety. The higher index indicates a wide margin between doses that are effective and doses that are toxic.