Transdermal Drug Delivery System of Linagliptin Sustained-release Microparticle Gels: In vitro Characterization and In vivo Evaluation

Background: Linagliptin (LNG) exhibits poor bioavailability and numerous side effects, significantly limiting its use. Transdermal drug delivery systems (TDDS) offer a potential solution to overcome the first-pass effect and gastrointestinal reactions associated with oral formulations. Objective: The aim of this study was to develop LNG microparticle gels to enhance drug bioavailability and mitigate side effects. Methods: Linagliptin hyaluronic acid (LNG-HA) microparticles were prepared by spray drying method and their formulation was optimized via a one-factor method. The solubility and release were investigated using the slurry method. LNG-HA microparticle gels were prepared and optimised using in vitro transdermal permeation assay. The hypoglycaemic effect of the LNG-HA microparticle gel was examined on diabetic mice. Results: The results indicated that the LNG-HA microparticle encapsulation rate was 84.46%. Carbomer was selected as the gel matrix for the microparticle gels. Compared to the oral API, the microparticle gel formulation demonstrated a distinct biphasic release pattern. In the first 30 minutes, only 43.56% of the drug was released, followed by a gradual release. This indicates that the formulation achieved a slow-release effect from a dual reservoir system. Furthermore, pharmacodynamic studies revealed a sustained hypoglycemic effect lasting for 48 hours with the LNG microparticle gel formulation. Conclusion: These findings signify that the LNG microparticle gel holds significant clinical value for providing sustained release and justifies its practical application.