Drug delivery to the anterior segment of the eye: A review of current and future treatment strategies

Development of Stable Tocopherol Succinate-Loaded Ethosomes to Enhance Transdermal Permeation: In-Vitro and In-Vivo Characterizations

BACKGROUND

Tocopherol succinate (TS) represents synthetic derivative of α-tocopherol (vitamin E), it act as anti-aging, moisturizing and antioxidant. Ultraviolet (UV) photo stability of TS is low and it cause skin irritation.

AIM

To develop tocopherol succinate loaded ethosomal gel for topical TS delivery and to evaluate its moisturizing and anti-aging effects.

METHOD

Cold method technique was used to produce ethosomal formulations (N=9) by varying ethanol and lipid concentrations (F1-F9). The most optimized formulation (F5) was selected for further study on the basis of characterization. F5 Formulation was incorporated into gel. Ex vivo permeation study was done by using Franz diffusion cell. Non-invasive in-vivo study was performed by using corneometer for evaluation of skin moisture content and skin mechanical properties by using cutometer, for 12 weeks on human subjects (N=13).

RESULTS

Particle size (PS), zeta potential (ZP) and polydispersity index (PDI), Entrapment efficiency were found to be 179.1 nm, -13.7 mV and 0.345, 99.71% respectively. TEM depicted spherical ethosomal particles. Ethosomal gel and control gel were evaluated for Conductivity and pH. Rheological analysis revealed a non-Newtonian flow. The release profile showed Initial burst and then sustained release, release data followed Korsmeyer-Peppas model. TS loaded ethosomal gel appeared physically stable and showed significant results in terms of skin capacitance and mechanical properties.

CONCLUSION

The prepared ethosomal gel formulation containing TS is more stable with enhanced antioxidant, moisturizing properties and increased TS deposition into the skin layer.

Topical drug delivery to the retina: obstacles and routes to success

INTRODUCTION

Retinal diseases are one of the main reasons for vision loss where all available drug treatments are based on invasive drug administration such as intravitreal injections. Despite huge efforts and some promising results in animal models, almost all delivery technologies tested have failed in human trials. There are however examples of clinically effective topical delivery systems such as fast dissolving aqueous eye drop suspensions.

AREAS COVERED

Six obstacles to topical drug delivery to the eye have been identified and discussed in some details. These obstacles consist of static membrane barriers to drug permeation into the eye, dynamic barriers such as the lacrimal drainage and physiochemical barriers such as low thermodynamic activity. It is explained how and why these obstacles hamper drug permeation and how different technologies, both those that are applied in marketed drug products and those that are under investigation, have addressed these obstacles.

EXPERT OPINION

The reason that most topical drug delivery systems have failed to deliver therapeutic drug concentrations to the retina is that they do not address physiochemical barriers such as the thermodynamic activity of the permeating drug molecules. Topical drug delivery to the retina has only been successful when the static, dynamic, and physiochemical barriers are addressed simultaneously.