In vitro permeation and stability studies on developed drug-in-adhesive transdermal patch of simvastatin

The transdermal drug-in-adhesive (DIA) patch of simvastatin (SM) was developed using acrylic adhesives such as DURO-TAK® 87-9301, DURO-TAK® 87-4287, DURO-TAK® 87-235A. The patches were evaluated for in vitro drug permeation across the pork ear skin using diffusion cell and stability studies. Among the three acrylic adhesives used, DURO-TAK® 87-9301 exhibited maximum flux (5.18 ± 0.23 µg/cm2/h). To further enhance the drug permeation, isopropyl myristate (IPM), d-limonene and 1,8-cineol as penetration enhancers (PEs) were incorporated into the DIA patch prepared from DURO-TAK® 87-9301. Out of those, IPM containing patch exhibited a flux of 16.45 ± 1.67 µg/cm2/h revealing that IPM is the best PE. The stability study was carried out on optimized fresh (SA4) and 6 months old patches stored at room and at accelerated condition (40 ± 2 °C/75 ± 5%RH) using FTIR, DSC and SEM techniques. Significant shift of peaks were not observed in FTIR spectra and DSC thermograms of the patches after the stability period. SEM micrographs of patches did not show any evidence of recrystallization indicating the presence of drug in the molecular form throughout the adhesive matrix. The investigation reveals that the DIA patch studied as above is stable and may serve as a potential drug delivery system for simvastatin.