In reply to Greg.

One of the objectives of pharmacokinetic studies is the determination of the area under the curve (AUC) parameter. The area under the curve represents the proportion of the drug absorbed into the systemic circulation and the time required to do so.

This pharmacokinetic parameter is used to determine the total exposure of a person to the drug over a period of time and is required by regulatory authorities to determine bioavailability and conclude bioequivalence or the absence of pharmacokinetic interactions.

The area under the curve can be obtained through two methodologies: the first involves nonlinear regression model analysis, or through non-compartmental analysis (NCA).

NCA is usually the preferred methodology as it requires fewer assumptions than model-based approaches. There are four methods to determine the AUC through non-compartmental analysis: Linear Log Trapezoidal, Linear Trapezoidal Interpolation, Linear Up Log Down, and Linear/Logarithmic Trapezoidal Interpolation.

The linear trapezoidal method uses linear interpolation between data points to calculate the AUC. This method is required by the OGD and the FDA, and it is the standard for bioequivalence trials.

The logarithmic trapezoidal method uses logarithmic interpolation between data points to calculate the AUC. This method is more accurate when concentrations are decreasing because drug elimination is exponential (making it linear on a logarithmic scale).

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