Formulation optimization of PVA/HPMC cryogel of Diltiazem HCl using 3-level factorial design and evaluation for ex vivo permeation

摘要

The aim of the present research was to optimize cryogel formulation of Diltiazem hydrochloride (DZ) with poly(vinyl alcohol) (PVA) and hydroxypropyl methylcellulose (HPMC) by utilizing response surface methodology followed by ex vivo permeation study on the optimized gel containing penetration enhancers. A 3-level factorial design was employed to formulate the experimental runs and to evaluate the effect of two independent variables such as the concentration of PVA and HPMC on characteristics of cryogel such as bioadhesive strength (BS) and in vitro drug release (dependent variables). Response surface plots such as contour and 3D plots were generated by the Design Expert? software to analyze the effect of independent variables on dependent variables. Fourier transform infrared spectroscopy studies confirmed the absence of interaction between DZ and polymers. Among various models generated by the software, quadratic model was found to be best fit for both the responses. Both the formulation factors influenced BS synergistically. However, the effect of HPMC concentration was more pronounced compared to concentration of PVA. But, an opposite effect shown by both the formulation factors on cumulative percentage of drug release (CPR) in 8 h. The optimized batch of cryogel of DZ selected by the software was having composition of 5 % of PVA and 2 % of HPMC. Penetration enhancers such as 1,8-cineole, d-limonene and carvone were incorporated into the optimized gel and permeation study was carried out using abdominal skin of rat. The study demonstrated a highest flux of 118 ± 5.81 μg/cm2/h in case of 1,8-cineole containing gel followed by carvone and d-limonene.