Tabriz University of Medical Sciences Pharmaceutical Sciences 1735-403X 32 3 2026 07 31 Kopexil vs Minoxidil: Exploring the Physicochemical Characteristics, Storage Stability, and Skin Permeability 451 461 10.34172/ps.43014 EN Sina Jalilzadeh https://orcid.org/0000-0002-9947-3283 Hamed Hamishehkar https://orcid.org/0000-0001-9905-0662 Farnaz Monajjemzadeh https://orcid.org/0000-0001-9369-5136 Journal Article 10.34172/ps.43014 2025 08 15 2025 10 09 Introduction: This study aimed to investigate the physicochemical properties, skin permeation behavior, and stability kinetics of Kopexil, a potential treatment for hair loss. Methods: Physicochemical characteristics of Kopexil were analyzed using Differential Scanning Calorimetry (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) spectroscopy, and High-Performance Liquid Chromatography (HPLC). Hydroalcoholic formulations (0.5%, 1%, and 2% Kopexil) were stored at 4 °C/60% RH, 25 °C/60% RH, and 40 °C/75% RH for 6 months, in accordance with ICH stability guidelines. HPLC method validation followed USP guidelines. In vitro skin permeation was assessed using Franz diffusion cells on full-thickness mouse skin. Tape-stripping followed by HPLC analysis quantified permeated drug levels. minoxidil served as a reference control in all assays. Results: DSC, FTIR, and UV-Vis spectra differentiated Kopexil from minoxidil. A validated HPLC method enabled precise analysis. Stability testing no physical changes in the formulations and t90%, which is the time required for the drug to retain 90% of its label claim was calculated. HPLC-UV analysis indicated t90% values of 39-50 and 20-42 months in different concentrations and different storage conditions, for kopexil and minoxidil, respectively. Kinetics evaluations confirmed zero-order degradation kinetics, indicating concentration-independent drug loss. Kopexil demonstrated a superior skin permeation rate compared to minoxidil and less drug deposited within the stratum corneum confirmed by tape-stripping. Conclusion: Kopexil was successfully characterized by multiple analytical techniques, distinguishing it from minoxidil. The results showed that the Hydro-alcoholic formulations of kopexil has slightly higher t90% values compared to minoxidil. Enhanced skin permeation of kopexil suggests potential advantage in topical alopecia treatment compared to minoxidil.