Drug effect-time profile

The time course of the drug effect including the onset, intensity and duration of effect is dependent on the drug concentration-time profile at the site of action.

The drug concentration-time profile at the site of action is dependent on the pharmacokinetic characters of the drugs.

It is usually impossible to measure the drug conc at the site of action, however this conc can be estimated from the pharmacokinetic model.

The relationship between the drug concentration at the site of action and the observed drug effect can be described by the pharmacodynamic models.

Duration of effect (A)
Intensity of effect (A) Onset of effect (A) MEC
Assuming that there is a certain
drug conc (MEC) that has to be
achieved at the site of action in
order to produce the effect
Duration of effect (B)
Intensity of effect (B) Onset of effect (B) MEC
Assuming that there is a certain
drug conc (MEC) that has to be
achieved at the site of action in
order to produce the effect
Drug B has faster onset, longer
duration, and produce more intense
pharmacological effect assuming that
the two drugs have the same potency.
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