Ethosomes entrapping salicylic acid were prepared using cold method and the effect of varying concentration of ethanol was considered for obtaining an optimized formulation. Lecithin (2%w/w) was used as the phospholipid to provide the structure to the vesicles and propylene glycol (10%) was used as the permeating agent. The vesicles were found to be of spherical to irregular shape ranged from 1.4 µm to 1.8 µm in size. The drug entrapment in the ethosomes was studied by analyzing the unentrapped drug using UV spectrophotometry at 310.4 nm and it was found that the maximum entrapment efficiency was found to be 92.07% for formulation ET3 and minimum 58.68% for formulation ET5, respectively. The in vitro permeation study suggested that the maximum permeation in the egg membrane occurred in ET3 (0.38 mg/cm²) with 30% ethanol concentration while ET5 exhibited the minimum permeation (0.28 mg/cm²). It was observed that only about 2% degradation occurred at room temperature and all formulations were almost stable at 8° and 4° with only 1.3% degradation of SA thereby proving the stability of the developed system. The best ethosomal formulation (ET3) was incorporated into gel base to obtain gel formulations and the results revealed a good protection of the ethosomal gel when 2% carbopol was used as the gelling base.

Ethosome, salicylic acid, gel, stability, lecithin, propylene glycol

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