Formulation & Evaluation of Transdermal Patch Containing Bilastine in Combination with Eucalyptol as Penetration Enhancer for Anti-Histaminic Activity

Allergic disorders such as rhinitis and urticaria are highly prevalent conditions that significantly impair quality of life. Bilastine, a second-generation non-sedating H1 antihistamine, is effective in controlling histamine-mediated symptoms but its oral administration is limited by poor aqueous solubility, variable gastrointestinal absorption, and first-pass hepatic metabolism, which reduce bioavailability. Transdermal drug delivery systems (TDDS) offer a promising alternative by providing controlled release, bypassing the gastrointestinal tract, and enhancing patient compliance. However, the stratum corneum poses a major barrier to drug permeation, necessitating the use of penetration enhancers. In this study, bilastine was incorporated into a transdermal patch along with eucalyptol (1,8-cineole), a natural monoterpene known to disrupt stratum corneum lipids and facilitate drug penetration. Eucalyptol was selected not only for its permeation-enhancing ability but also for its anti-inflammatory and antioxidant properties that may complement bilastine’s therapeutic action. The formulated patches were evaluated for physicochemical characteristics, drug content uniformity, tensile strength, flexibility, and moisture balance. In-vitro release and permeation studies were conducted to assess drug delivery performance. The results demonstrated that bilastine patches with eucalyptol exhibited satisfactory physicomechanical properties, uniform drug distribution, and sustained release. Eucalyptol significantly enhanced skin permeation of bilastine compared to control formulations. These findings suggest that the bilastine–eucalyptol transdermal patch provides improved drug bioavailability, prolonged therapeutic activity, and reduced dosing frequency compared to oral therapy. In conclusion, the study highlights the potential of bilastine-loaded transdermal patches with eucalyptol as a safe, effective, and patient-friendly approach for long-term management of allergic disorders.