Preparation of transdermal monolithic systems of indapamide by solvent casting method and the use of vegetable oils as permeation enhancer

Transdermal drug delivery systems of indapamide have been formulated by using solvent casting method. Monolithic systems were prepared by using hydroxy propyl methyl cellulose (HPMC) and ethyl cellulose (EC) polymers by incorporating glycerine and dibutyl phthalate as plasticizers, respectively. All the patches were uniform with respect to physicochemical and scanning electron microscopy (SEM) evaluation. The in vitro drug release studies indicated that HPMC containing films have shown better release than that of EC containing films without any permeation enhancer. A total of eight monolithic systems were prepared by using a drug polymer ratio of 1:4 and incorporated different vegetable oils as permeation enhancers in different concentrations. The prepared systems released the drug in the following order: F3 > F4 > F7 > F5 > F8 > F6 > F1 > F2. The various permeation parameters such as flux, permeability coefficient, enhancement ratio and diffusion rate constants were determined for all the formulations. The maximum flux of 9.08 x 102 mg/cm2 h was observed with HPMC monolithic system containing 30% w/w olive oil. A significant improvement of flux was observed in the following order: olive oil > linseed oil > sunflower oil > cottonseed oil > coconut oil > castor oil. Further improvement of flux was observed, when 30% w/w olive oil was applied directly onto the skin prior to the studies. The in vitro release studies revealed that the release was sustained up to 24 h and it follows zero-order kinetics. All the films were found to be stable at 37°C and 45°C with respect to their physical parameters and drug content.