Film-Forming Gels for Topical Drug Delivery: A Systematic Review of the Effects of Formulation on Film Performance, Drug Release, and Skin Permeation

Film-forming gels (FFGs) are increasingly recognized as a medium for topical drug delivery. However, existing evidence correlating specific formulation characteristics with drug delivery efficacy remains fragmented across many studies and is only partially organized. This systematic review aimed to consolidate these findings into a single framework and examine how important formulation variables affect three main outcome domains: film characteristics, drug release behavior, and skin permeation. A systematic search of PubMed and Scopus was conducted until October 2025, adhering to the PRISMA criteria. Studies were included if they examined topical FFG formulations and reported at least one of the predetermined outcomes. A total of 27 studies fulfilled the inclusion criteria, with solvent evaporation identified as the predominant method for FFG preparation. Across this body of research, the selection and relative ratio of polymers and plasticizers have consistently emerged as critical determinants influencing drying time (