JOURNAL OF COSMETIC SCIENCE 76 provided in Figures 1–3. These fi gures show the amount of drug delivered with respect to time and area (fl ux) across the cadaver epidermis. On comparing with drug delivered by the commercial products, the silicone elastomer– based prototype formulations delivered either equal and in most cases higher amount of the drug across the skin epidermis. The silicone formulation (SiE1) released about 3× DCF (5.92 ± 0.5 μg vs 2.01 ± 0.7 μg) cumulatively in an 8-h period while showing compa- rable release profi le. Irrespective of very low concentration of the drug CLP, the SiE2- based silicone formulation delivered over double the amount (5181 ± 1457 ng vs 2128 ± 218 ng) delivered by commercial product cumulatively in a 26-h period. The SiE1-based silicone formulation delivered a similar amount (2431 ± 591 ng vs 2128 ± 218 ng) to that of benchmark cumulatively at the same 26-h period. The SiE1-based LDC formula- tion delivered about 2× (146.4 μg vs 60.6 μg) amount compared with the benchmark. DISCUSSION AND CONCLUSION The active-loaded formulations based on silicone elastomer blend technologies delivered drugs effectively across the skin in vitro. The study data support the concept that topical Table I Composition of the Silicone Elastomer Blend Formulations Ingredient SiE1-CLP gel SiE2-CLP gel SiE1-DCF-gel SiE1-LDC gel % (w/w) SiE1 60.47a - 69.3 66.5 SiE2 - 74.90a - - Propylene glycol 9.57 6.73 7.1 6.8 Oleic acid 1.06 0.75 0.8 0.8 Isopropyl alcohol 28.85 17.57 21.8 20.9 CLP 0.05 0.05 - - DCF - - 1.0 - LDC - - - 5.0 aElastomer blends with 26% solids were utilized. Figure 1. Flux profi les of Si formulation containing 0.05% w/w CLP compared with commercial benchmark.

SILICONE ELASTOMER BLENDS 77 formulations using silicone elastomer as excipients can deliver different types of drugs including NSAIDs or steroids effi ciently. As silicone elastomer-based formulations provide improved aesthetics for beauty care ap- plications, similar formulations may enhance patience compliance in topically applied over-the-counter medicated or pharmaceutical drug products. While historically used in skin care because of their sensory benefi ts, different cross-link chemistries, and a range of carrier solvents, silicone elastomer technologies have allowed for broader compatibility with a range of excipients and drug classes including NSAIDs, potent corticosteroids, and topical anesthetics. Beyond their aesthetics, the silicone elastomer family should be recognized as a novel topical drug delivery platform and provides the ability to formulate a variety of drugs in physically stable formulations. In general, the silicone-based formulations delivered about 2–3× of drugs compared with respective commercial product. These prototype formulations were not fully optimized toward any product development however, we believe that there may still be room to improve the drug delivery. It is to be noted that silicone formulation which contained CLP at 0.05% delivered more than twice drug compared with the commercial product. The results indicate that silicone elastomer blend formulations have the capability to show effi cient drug delivery even when the formulations had very low drug concentrations. We have introduced a novel silicone topical drug delivery platform that builds on his- torical sensory advantages of silicones, but combines the advantages of both silicone and Figure 3. Flux profi les of Si formulation containing 5% w/w LDC compared with commercial benchmark. Figure 2. Flux profi les of Si formulation containing 1% w/w DCF compared with commercial benchmark.