Silica-based microencapsulation used in topical dermatologic applications.

Microencapsulation has received extensive attention because of its various applications. Since its inception in the 1940s, this technology has been used across several areas, including the chemical, food, and pharmaceutical industries. Over-the-counter skin products often contain ingredients that readily and unevenly degrade upon contact with the skin. Enclosing these substances within a silica shell can enhance their stability and better regulate their delivery onto and into the skin. Silica microencapsulation uses silica as the matrix material into which ingredients can be embedded to form microcapsules. The FDA recognizes amorphous silica as a safe inorganic excipient and recently approved two new topical therapies for the treatment of rosacea and acne. The first approved formulation uses a novel silica-based controlled vehicle delivery technology to improve the stability of two active ingredients that are normally not able to be used in the same formulation due to potential instability and drug degradation. The formulation contains 3.0% benzoyl peroxide (BPO) and 0.1% tretinoin topical cream to treat acne vulgaris in adults and pediatric patients. The second formulation contains silica microencapsulated 5.0% BPO topical cream to treat inflammatory rosacea lesions in adults. Both formulations use the same amorphous silica sol-gel microencapsulation technology to improve formulation stability and skin compatibility parameters.

Microencapsulated Benzoyl Peroxide and Tretinoin for the Treatment of Acne Vulgaris: Results from a Phase 2 Multicenter, Double-Blind, Randomized, Vehicle-Controlled Study.

This phase 2, 12-week, multicenter, randomized, double-blind, active- and vehicle-controlled (VC), parallel-group trial assessed the efficacy and safety of silica encapsulated benzoyl peroxide BP (E-BP), two concentrations of silica encapsulated tretinoin (E-ATRA) and their combinations (TWIN high and low) vs VC in 726 males and females ≥9 years of age with moderate-to-severe inflammatory facial acne. The co-primary efficacy endpoints were Investigators Global Assessment (IGA) success rate ("clear" or "almost clear") and changes from baseline in inflammatory and non-inflammatory lesion counts. TWIN high and low were each significantly superior vs VC for IGA success at 12 weeks (39.7% and 27.4%, respectively, vs 12.3%, P < 0.001 and P < 0.01). TWIN high and low resulted in mean reductions in inflammatory lesions of -16.9 (64%) and -17.0 (60.8%) vs -11.5 (42%) for VC. Reductions in non-inflammatory lesions were -23.7 for TWIN low (54.9%) and -23.6 for TWIN high (53.3%) vs -13.7 (32.4%) for VC (all P < 0.001 vs VC). Results for TWIN were also numerically superior to E-BP and E-ATRA. All treatments were safe with comparable skin tolerability. The significant superiority of both combinations over VC and numerical superiority over E-BP and E-ATRA were achieved without an increase in adverse events or reduced skin tolerability.

A look at emerging delivery systems for topical drug products.

The introduction of new topical drugs based on new chemical entities has become a rare event. Instead, pharmaceutical companies have been focused on reformulating existing drugs resulting in an ever-growing number of topical drug products for every approved drug substance. In light of this trend, soon reformulations may not be as rewarding to their sponsors as they are today unless they offer a substantial improvement over other formulations of the same drug substance and the same indication, namely improved efficacy over existing drugs, reduced side effects, unique drug combinations, or applicability for new indications. This article reviews and compares topical drug delivery systems currently under active research that are designed to offer such advantages in the coming years. The reviewed delivery systems are: liposomes, niosomes, transferosomes, ethosomes, solid lipid nanoparticles, nanostructured lipid carriers, cyclodextrin, and sol-gel microcapsules. Among all the topical drug delivery systems currently undergoing active research, only the sol-gel microencapsulation is at clinical stages.