In pharmaceutical development, it's crucial to establish a predictive in vitro–in vivo correlation (IVIVC) for two or more formulations to gain a comprehensive understanding of release properties. IVIVC reduces the need for costly in vivo studies and facilitates the establishment of meaningful dissolution specifications with significant cost savings and decreased regulatory burden. Furthermore, a meaningful IVIVC should predict Cmax and AUC within 20%, aligning with FDA guidance while adhering to internal and external predictability criteria. The categorization of IVIVC into Level A, B, and C correlations provides distinct insights into the relationship between in vitro dissolution and in vivo performance, aiding in justifying manufacturing changes and fostering formulation development.
The main objective of developing and evaluating a IVIVC is to establish the dissolution test as a substitute for in vivo bioavailability studies in humans. This has several applications, including ensuring batch-to-batch consistency, aiding in new dosage form development, and validating dissolution specifications based on in vivo performance. Two key approaches to developing IVIVC involve establishing linear relationships between in vitro dissolution and in vivo bioavailability parameters and modifying dissolution methodology using previous bioavailability data.
The relationship between dissolution rate and absorption rate is vital in understanding the drug's behavior, where a faster dissolution rate may lead to a quicker appearance of the drug in the plasma. This study was exemplified in the analysis of three sustained-release aspirin products, revealing a linear correlation between dissolution times and absorption times, indicating the significant impact of the dissolution rate on the rapid absorption of aspirin.
Moreover, the correlation of serum drug concentration with the percent of drug dissolved highlights the intricate interplay between in vitro dissolution and in vivo absorption, showcasing how various formulations with different dissolution rates can cause differences in serum drug concentration. Additionally, the biopharmaceutic drug classification system (BCS) provides a predictive approach to relate the physicochemical characteristics of a drug substance and product to in vivo bioavailability, particularly for immediate-release oral drug products meeting the criteria for BCS Class I drugs.
Overall, understanding IVIVC and its implications for formulation development and bioavailability is pivotal in optimizing pharmaceutical products' performance and ensuring their efficacy in clinical settings.
In vitro–in vivo correlation is a predictive mathematical model demonstrating the relationship between in vitro drug properties and a relevant in vivo response.
The correlation is defined at three levels.
Level A correlation represents a point-to-point correlation between in vitro dissolution and in vivo absorption, justifying manufacturing and formulation changes without additional human studies.
Level B correlation utilizes statistical moment analysis to compare the mean in vitro dissolution time to the mean in vivo dissolution. Still, this correlation method alone cannot justify manufacturing changes, formulation modification, and batch-to-batch quality.
Level C correlation relates one dissolution time point to one pharmacokinetic parameter and helps develop formulations.
Multiple level C correlation links one or multiple pharmacokinetic parameters to the drug quantity dissolved at different time intervals.
In a study with three sustained-release aspirin products, the dissolution times were linearly correlated to absorption times, indicating the dependence of aspirin’s rapid absorption on the dissolution rate.
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