Question

What's the pA₂ value of an antagonist and how does this relate? to pK_B? (Topic: Pharmacodynamics)

Answer 1

A pA2 value is used in the field of biochemistry. It determines the relationship between two drugs competing for effect on the same receptor. The drug which is agonist tries to affect the receptor. The antagonist drug tries to block the agonist from working. The two drugs are competitive if increasing or reducing one drug decreases or increases the effect of the other , respectively. The pa2 value indicates the concentration of antagonist when double agonist is required to have the same effect on the receptor as when no antagonist is present.