Combined use of borneol or menthol with labrasol promotes penetration of baicalin through rabbit cornea in vitro.

The permeability of most drugs through the eyes is very limited, so finding safe and effective penetration enhancers is of high importance in current ophthalmology research. In this paper, we use a new approach that integrates Chinese and Western medicine to improve the corneal permeability of baicalin, a water- and fat-insoluble target drug, in vitro. Rabbits were divided into three groups. The first group was dosed with borneol (0.05%, 0.1%). menthol (0.1%, 0.2%), or Labrasol (1%, 2%) individually, the second was dosed with a combination of Labrasol with either borneol or menthol, and the third group received a control treatment. Compared with the control treatment, borneol, menthol, or Labrasol alone clearly improved the permeability of baicalin in vitro. Furthermore, the penetrating effects were significantly increased by combining the application of Labrasol with menthol or borneol. Among the various combined penetration enhancers, 0.1% borneol with 2% Labrasol achieved the best apparent permeability, approximately 16.35 times that of the control. Additionally, the calculation of corneal hydration level and the Draize test demonstrated the safety of these penetration enhancers to the rabbit corneas in vivo. This study confirms that the combined use of borneol or menthol, compounds both derived from Chinese herbs, with Labrasol can improve the corneal permeability of water- and fat-insoluble drugs.