As pA2 increases, the antagonist becomes more potent.
An antagonist with a pA2 of 4 requires a concentration of 1 x 10-4 M to reduce the effect of a double dose of agonist to that of a single dose.
An antagonist with a pA
2 of 8 requires a concentration of
1 x 10
-8 M to reduce the effect of a double dose of agonist to that of a single dose
ie a much lower concentration of antagonist is needed to half the agonist's response.