Exploring the relationships between scaled bioequivalence limits and within-subject variability

Area of Science:

• Pharmacokinetics and Pharmaceutical Sciences
• Regulatory Science
• Biostatistics

Background:

• Assessing bioequivalence (BE) for drugs with high within-subject variability poses significant challenges.
• Traditional BE methods require large sample sizes, increasing costs and time.
• Scaled bioequivalence limits (BELs) have emerged as a key regulatory strategy to address this challenge.

Purpose of the Study:

• To provide a comprehensive analysis of scaled bioequivalence limits (BELs) and their dependence on drug variability.
• To elucidate the mathematical relationships governing scaled BELs.
• To understand the causal differences in how various scaled BEL approaches handle variability.

Main Methods:

• Comparative analysis of scaled BELs using algebraic manipulations.
• Graphical illustrations to visualize BEL behavior.
• Emphasis on "absolute change" and "relative change" metrics to quantify BEL expansion.

Main Results:

• Demonstrated how scaled BELs expand with increasing drug variability.
• Identified distinct mathematical relationships underlying different scaled BEL approaches.
• Quantified the "absolute" and "relative" changes associated with each scaled BEL, revealing causal differences.

Conclusions:

• The study provides critical insights into the performance of scaled bioequivalence limits based on their mathematical properties.
• Understanding the "absolute" and "relative" changes is key to differentiating scaled BEL approaches.
• Findings align with observed practical performance differences among various scaled BE strategies, aiding regulatory decision-making.