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Study designs Basic PK concepts and measurements77 Basic PK concepts and measurements77

Area under the curve (AUC)

The overall amount of drug in the bloodstream after a dose

Generating an AUC requires collecting many blood samples (usually every one or two hours) right after a person takes a dose up until the next dose is due


Measures of the amount of intact drug that reaches the systemic circulation

Provides information about the dose/dosage regimen and performance of different formulations


Formulations containing the same dose of the same chemical entity, generally in the same dosage form, and that are intended to be interchangeable are deemed bioequivalent

This information may be useful for evaluating formulation changes (tablet vs. capsule) and comparing generic and branded drugs

Drugs that are bioequivalent are not expected to differ in clinical and adverse events

(maximum concentration)

The highest concentration of drug in the blood that is measured after a dose

Cmax usually happens within a few hours after the dose is taken

The time that Cmax happens is referred to as Tmax

Cmin or trough
(minimum concentration)

The lowest concentration of the drug in the blood that is measured after a dose

It happens right before a patient takes the next usual dose

Half-life (t½)

The amount of time it takes for the drug concentration in the blood to decline by half

t½ is one of the most important PK measurements for how often a drug has to be dosed


77. Anderson PL. The ABCs of Pharmacokinetics. The Body. Winter 2005. Available at

78. Arons L. Vasic Concepts in Pharmacokinetics. Available at