Bioequivalence of Topical Products; Past, Present and Future

As doctors, pharmacists, and health care professionals, we are regularly confronted with the increasing disparity and decreasing affordability of quality lifesaving medications, including topical dermatological products. This is seen to be further imbalanced in countries such as the United States where public funded support is behind global levels. Generic products can be safe and effective alternatives. However, regulatory approvals of generic topical products lag behind the market requirements due to a lack of appropriate technologies that can assess drug levels at the site of action. In the absence of these, clinical equivalence studies (clinical trials) continue to be a gold standard. There is renewed hope and optimism as both European and American regulators have demonstrated through recent efforts that change could be around the corner. Newer and less expensive regulatory tools are being tried and evidence is continually compiled to validate their utility.

Assessment of bioequivalence in topical pharmaceutical products has proved to be a challenge due to the complex nature of skin as a barrier, the variability in skin from person to person and from one body site to another. This special edition with a central focus on the bioequivalence of topical products, will describe past, present and upcoming approaches to bioequivalence, in particular a collection of research articles, reviews and commentaries exploring methods, early proofs and validating established techniques to promote investigation into alternative approaches to bioequivalence. We envisage that this effort will help gather crucial literature, results and discuss the various methodologies utilized to assess topical product bioequivalence in one unique collection of high-quality research. It is our goal to help the industry and academia gain access to open source data pertaining to the field, where it can be of most benefit.

This special edition invites all types accepted by the section Translational Pharmacology (full articles, reviews, commentaries, protocols etc.) for publications describing topical product bioequivalence. This includes but is not limited to publications on clinical equivalence studies (clinical efficacy studies), novel in vivo approaches such as dermatopharmacokinetics, dermal microdialysis, dermal open flow microperfusion, imaging/tomography-based assessment techniques, ex vivo approaches and in vitro approaches. Within in vitro approaches, recent emphasis has seen a renewed interest on characterization of critical quality attributes of topical products. Novel and established methods demonstrating assessment of CQAs for BE in combination with in vitro permeation testing (IVPT) and in vitro release test (IVPT) are welcome. The full scope of the special edition also includes rheological characterisations etc. for comparative assessment of topical products, their similarities, and differences.