Formulation design and development of matrix diffusion controlled transdermal drug delivery of glimepiride

Background: The present work was conducted to prepare and evaluate transdermal patches with optimization of suitable polymeric blend of poly(meth) acrylates (Eudragit (R)) (Ammonio Methacrylate Copolymer Ph Eur) for sustained transdermal delivery of glimepiride. Method: Polymeric matrix transdermal films were prepared by using Ammonio Methacrylate Copolymer Ph Eur RL 100 and Ammonio Methacrylate Copolymer Ph Eur RS 100 as the film former, and dibutyl phthalate (30% w/w) as the plasticizer. Patches were characterized by physical appearance, thickness, weight variation, folding endurance, percentage erosion, swelling index, moisture content, and moisture uptake capacity. Fourier transform infrared spectroscopic studies and differential scanning calorimetry analysis of physical mixtures of contents were performed to identify any chemical and physical interaction between drug and excipients. Five different enhancers (isopropyl myristate [IPM], Span (R) 80, Tween (R) 20, eucalyptus oil, and limonene) were employed at three different concentrations of polymer (2%, 5%, and 10% w/w) in order to enhance permeation through rabbit skin. In vitro drug release studies were performed at pH 7.4, and scanning electron microscopy was conducted to elucidate surface morphology before and after the drug release. In vitro permeation studies through rabbit skin were performed on Franz diffusion cells and permeation kinetics followed the Higuchi model. Results: Results of in vitro permeation studies revealed that these enhancers not only increased drug release but also augmented the skin permeation of glimepiride. Conclusion: IPM was the most effective enhancer with the highest permeation flux of 51.763 mu g/cm(2)/hr, and the enhancement effect of different enhancers on glimepiride permeation through rabbit skin was in the rank order of IPM > eucalyptus oil > Span (R) 80. Tween (R) 20. limonene.