Partial agonists competitive antagonism

Two agonist drugs with different intrinsic activities exert their actions at the same receptor site let the full agonist A he a drug with the intrinsic activity a = L In the partial agonist B, let the intrinsic activity P be less than 1. The interaction described above as pure competitive antagonism represents nothing other than the extreme situation P = 0. 

If the antagonism is insurmountable, then there are a number of molecular mechanisms possible. The next question to ask is if the maximal response to the agonist can be completely depressed to basal levels. If this is not the case, then there could be partial allosteric alteration of the signaling properties of the receptor. Alternatively, this could be due to a hemi-equilibrium condition that produces a partial shortfall to true competitive equilibrium, leading to incomplete depression of the maximal response but also antagonist concentration-related dextral displacement of the concentration response curve to the agonist (see Figure 10.19a). The model (see Section 10.6.5) used to fit these data is discussed in Section 6.5 and shown in... 

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