Area Under the Curve (AUC)

The Area Under the Curve (AUC) is a critical parameter in pharmacokinetics, representing the integral of the drug concentration-time curve. It quantifies the total drug exposure over time, providing vital information on drug absorption, distribution, metabolism, and elimination.

Definition

${\text{AUC}}=\int _{0}^{\infty }C(t)\,dt$

Where:

• $C(t)$ is the drug concentration at time $t$

AUC offers insight into the extent and rate of drug absorption, making it a fundamental measure to assess bioavailability and bioequivalence of drugs.

Types of AUC

Several types of AUC values exist, each serving unique purposes in pharmacokinetic studies:

Type	Description	Application
${\text{AUC}}_{\text{last}}$	Area under the concentration-time curve up to the last measurable concentration.	Used to determine the total exposure of the body to the drug until the last measurable concentration.
${\text{AUC}}_{0\to \infty }$	Represents the total area under the concentration-time curve from administration to infinity.	Provides an estimate of the total exposure of the body to a drug. Useful for evaluating the overall efficacy of a drug.
${\text{AUC}}_{0\to t}$	Area under the concentration-time curve from the administration up to a specific time 't'.	Useful for focusing on drug exposure within specific time windows.
${\text{AUC}}_{0\to 24}$	Area under the concentration-time curve from administration up to 24 hours.	Often used when drugs are administered once a day.
${\text{AUC}}_{\tau }$	Area under the concentration-time curve over a dosing interval 'tau', for example in repeated dosing every 12 or 24 hours.	Helpful in evaluating steady-state pharmacokinetics in multiple dosing regimens.
${\text{AUC}}_{\text{micro}}$	Utilizes microdosing studies and mass spectrometric analyses to determine the AUC for drugs administered in very low concentrations.	Suitable for studying the pharmacokinetics of drugs at subtherapeutic, micro-level doses.

Application

AUC is indispensable in pharmacology and drug development:

• It is pivotal for determining the dosage and frequency of drug administration.
• It aids in evaluating the bioequivalence of generic drugs to brand-name counterparts.
• It enables researchers to study the pharmacokinetics of new drug candidates.

See Also

• Pharmacokinetics
• Drug Metabolism
• Bioavailability
• Bioequivalence