Partial Area Under the Curve: A Revelatory Story in Pharmacokinetics.

Bioequivalence studies are important for a generic drug to enter the market. These studies mainly examine various pharmacokinetic parameters like Cmax, AUC0-T and AUC0-∞. But at times, these parameters might not be sufficient to pick up essential kinetics. It is even possible to undertake the additional parameter along with the traditional pharmacometrics. This article gives an overview of one such parameter, partial area under the curve (pAUC), which captures specific time intervals of clinical relevance. The pAUC is especially useful for comparing specific formulations, determining bioequivalence in early or late stages, and assessing medicines with time-dependent therapeutic windows. When employed correctly, pAUC improves our understanding of temporal drug behaviour beyond what total AUC can provide, allowing for more precise and clinically meaningful pharmacokinetic assessments. This article is a review that describes how pAUC has been used in specific regulatory guidelines for drug products that have time-dependent exposures, which may impact the drug's pharmacodynamic properties. These product guidances have been issued by the US Food and Drug Administration (FDA), Health Canada, and European Medicines Agency (EMA). This article presents various viewpoints about pAUC in the mindset of regulators, researchers, and industrial experts.