Experimental design for optimizing drug release from silicone elastomer matrix and investigation of transdermal drug delivery

Silicone elastomers are commonly used for medical devices and external prosthesis. Recently, there has been growing interest in silicone-based medical devices with enhanced function that release drugs from the elastomer matrix. In the current study, an experimental design approach was used to optimize the release properties of the model drug diclofenac from medical silicone elastomer matrix, including a combination of four permeation enhancers as additives and allowing for constraints in the properties of the material. The D-optimal design included six factors and five responses describing material properties and release of the drug. The first experimental object was screening, to investigate the main and interaction effects, based on 29 experiments. All excipients had a significant effect and were therefore included in the optimization, which also allowed the possible contribution of quadratic terms to the model and was based on 38 experiments. Screening and optimization of release and material properties resulted in the production of two optimized silicone membranes, which were tested for transdermal delivery. The results confirmed the validity of the model for the optimized membranes that were used for further testing for transdermal drug delivery through heat-separated human skin. The optimization resulted in an excipient/drug/silicone composition that resulted in a cured elastomer with good tensile strength and a 4- to 7-fold transdermal delivery increase relative to elastomer that did not contain excipients.