Merck Manual

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Log-concentration vs response curves
Log-concentration vs response curves

    Log-concentration vs response curves for full agonists with 2 affinities and a partial agonist. The solid line traces the effect of a full agonist. Because the same maximal response is achieved, the drug represented by the dashed line is also a full agonist; however, it has a lower potency (presumably due to decreased receptor binding affinity). The dotted line shows the curve for a partial agonist. Notice that it has a lower Emax than the other 2 drugs. Also, the EC50 of this curve shows that this partial agonist has the same potency (EC50 = 10) as the full agonist shown in the solid line but a higher potency than the full agonist shown with the dashed line (EC50 = 100).

Courtesy of Dr. Duncan C. Ferguson.