# Refining Bioequivalence Assessment of Topical Drug Products for Local Action: A Comparative Analysis of Tape Stripping Methodologies

## TL;DR

This paper compares different tape stripping methods for assessing bioequivalence of topical drugs, suggesting simpler single time point studies are sufficient.

## Contribution

The paper proposes that single time point uptake studies are more practical and sufficient for bioequivalence assessments of topical drugs.

## Key findings

- Clearance time measurements add little value for topical drugs acting locally in the skin.
- Single time point uptake studies are more convenient and sufficient for regulatory assessments.
- The paper provides practical guidance for bioequivalence assessment of topical dermatological products.

## Abstract

Tape stripping (TS) is a minimally invasive technique that enables in vivo assessment of drug uptake in the skin of human subjects. Whilst appropriate for evaluating the bioequivalence (BE) of topical formulations, methodological variations persist, especially regarding the inclusion of clearance time measurements. This manuscript compares the TS protocols described in several publications, including the European Medicines Agency (EMA) and Japanese guidance, containing information relating to the evaluation of utility, practicality, and scientific validity. Evidence suggests that for drugs acting locally in the skin, clearance measurements that require time-consuming practical manipulation and subsequent complex data processing offer limited value, whereas single time point uptake studies, which are more convenient and expedient, may suffice for regulatory BE assessments. This discussion offers practical guidance for BE assessment of topical dermatological products and a more expedient approach using a single time point uptake study protocol, obviating the need for clearance time assessments.