drugs
Drug Action
Affinity and Intrinsic Activity of Drugs
A drug’s action is affected by the quantity of drug that reaches the receptor and the degree of attraction (affinity) between it and its receptor on the cell’s surface. Once bound to their receptor, drugs vary in their ability to produce an effect (intrinsic activity). A drug's affinity and intrinsic activity are determined by its chemical structure. Drugs that activate receptors ( Agonists and antagonists ) must have both great affinity and intrinsic activity: They must bind effectively to their receptors, and the drug bound to its receptor (drug-receptor complex) must be capable of producing an effect in the targeted area. In contrast, drugs that block receptors ( 