Advances in Characterization of Transdermal and Topical Products using Texture Analyzer Systems.

The efficacy, safety, and stability of transdermal and topical products (TTPs) are of prime importance to consumer acceptance and compliance. To control the consistent textural quality or overall physical properties of TTPs, texture analysis tests are widely applied to assess potential changes in features and internal structure of products throughout different stages of formulation development, manufacturing, and distribution. As one of the essential texture test types, Texture Profile Analysis (TPA) provides critical insights into the structure, spreadability, adhesion, sensory attributes, and consistency of semisolid formulations via key measured parameters such as hardness, adhesiveness, cohesiveness, elasticity, and compressibility. Recent advancements in automation and multimodal analysis have enhanced the precision and applicability of TPA. For transdermal delivery systems (TDS), adhesion, a critical quality attribute (CQA), which is influenced by viscoelasticity, surface energy, and wetting characteristics of pressure-sensitive adhesives (PSAs), can be assessed through in vitro methods like peel, tack, and shear tests using texture analyzer systems. While in vivo assessments remain subjective, in vitro tests conducted by texture analyzers enable standardized and reproducible evaluations, ensuring reliable comparisons across products and bridging gaps between laboratory and real-world performance. Microneedles (µNDs), another innovative transdermal platform, require robust mechanical strength to ensure effective skin penetration and drug release. Texture analysis plays a pivotal role in characterizing critical properties such as hardness, flexibility, and puncture strength, simulating forces encountered during skin penetration. This analysis offers valuable insights into µND performance, ensuring safety, functionality, and patient compliance. This review systematically curates existing knowledge on using texture analyzers to measure textural properties of pharmaceutical TTPs while highlighting emerging trends and providing methodologies for testing and parameter derivation. By emphasizing the importance of CQA characterization for novel drug delivery platforms, this work underscores the role of texture analysis in optimizing designs of TTPs including µND, focusing on fracture, insertion, and bending forces, ultimately contributing to the development of safer and more efficient transdermal systems.