Pharmacodynamic models

3- The Emax model

This model assumes that the effect of the drug increases as the drug conc increases until it reaches a plateau (maximum effect) at very high drug conc.

E =

Emax C

EC50 + C
Emax

1

2E max
EC50

This model can also account for the existence of a baseline effect in absence of the drug:

E = E0 +

Emax C

EC50 + C
We maximum effect is the difference between the maximum
measured value and the baseline effect EC50 Emax E0

The model can be used when the drug causes reduction in the value of the measured effect.

E = E0 -

Emax C

EC50 + C
The maximum effect is difference between the baseline
effect and the minimum measured value. EC50 Emax E0
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