Dermal patches for the controlled release of miconazole: Influence of the drug concentration on the technological characteristics

The aim of this work was to evaluate the effect of different amounts of miconazole nitrate (MIC) on the technological characteristics (drug release profile, adhesiveness, and water vapor permeability) of a nonocclusive dermal therapeutic system (DTS) for the treatment of tinea unguium infection. Artificial silk was used as a backing layer. The self-adhesive matrix was made of a mixture of Plastoid® E 35 L (PL L), an adhesive hydrophilic polymer, and Eudragit® NE 40 D (EU NE), a nonadhesive hydrophobic polymer able to modify the drug release. Plastoid E 35 L is a copolymer of dimethylaminoethyl methacrylate and neutral methacrylic ester. Eudragit NE 40 D is a copolymer of ethylacrylate and methylmethacrylate. Formulations containing different amounts of MIC, ranging from 2% to 16% w/w of the dried matrix, were designed. Drug crystals were observed by polarizing light microscopy, proving the incomplete solubilization of MIC only in the matrices containing 8% w/w or more of this compound. All systems provided an in vitro control of drug release for at least 24 hr. The amount of the drug released increased with drug loading in all DTS. The percentage of the drug released was the same in all the DTS containing detectable crystals of MIC. When the MIC was completely dissolved in the matrix, the released percentage decreased when drug loading increased. The water vapor permeability and the adhesive properties of the DTS were excellent.