Application of viscometry and solubility parameters in miconazole patches development

Nine binary mixtures of seven different methacrylic copolymer systems (Plas toid(R) E 35 L (PLE) and Plastoid(R) L 50 (PLL); Eudragit(R) (Eu) NE, RL, R S, L, S) were tested as components of monolayer patches containing miconazo le. Only three mixtures (PLE:EuNE, PLE:EuRL and PLE:EuRS) were suitable for the preparation of placebo matrices. Miconazole parches with good technolo gical characteristics were obtained by using mixtures of PLE:EuNE and PLE:E uRL. The in vitro miconazole release rate from the two patches and from the patch prepared using only PLE were significantly different. The amounts of drug released in 24 h were quits satisfactory. A mathematical model based on capillary viscometry data was used for the evaluation of interactions be tween copolymers. This was useful to predict and understand the mechanisms related to the instability of the prepared mixture. The solubility paramete rs of thr drug and of the matrix were also calculated. Miconazole release w as faster when the difference between the solubility parameters of the matr ix and of the drug was higher. A relationship between miconazole release ra te and the difference of drug and matrix solubility parameters was found. T herefore, the solubility parameter could be applied in formulation studies of patches. (C) 1999 Elsevier Science B.V. All rights reserved.