Formulation and evaluation of novel vesicular nanoethosomal patches for transdermal delivery of zidovudine: In vitro, ex vivo, and in vivo pharmacokinetic investigations

Ethosomes are novel soft malleable nanovesicles composed mainly of phospholipids, ethanol (relatively high concentration), glycol, and water. They are used for enhanced drug delivery through the skin. These zidovudine (ZV) vesicles were formulated by cold technique using phospholipids, cholesterol, propylene glycol, and ethanol. The nanoethosomal dispersion was transformed to transethosomal patches using HPMC E15 and chitosan as polymers, a mixture of dichloromethane (DCM) and methanol (1:1 ratio) as solvent, triethyl citrate as plasticizer, and span 80 as permeation enhancer. The physical features of the prepared patches were found to be within acceptable limits. The in vitro study showed drug diffusion of 71.25 - 88.19% through the semipermeable egg membrane in 24 hours. The ex vivo study showed drug permeation of 78.35 - 91.45% through the goat ear membrane in 24 hours. The combination of HPMC and EP4 transdermal patch was determined to be the most effective formulation for transdermal drug administration with sustained drug release, outperforming all other formulations based on acceptable physicochemical parameters, in vitro and ex vivo evaluation studies. Compared with the other formulations, the EP4 formulation had superior penetration kinetics, as proven by its highest permeation co-efficient (2.56 mg/cm2/h), flux (0.494 mg/cm2/h), and enhancement ratio (2.43). Moreover, dermal irritation tests demonstrated that topical therapy did not cause any irritation, indicating its safety. The in vivo bioavailability studies revealed that the AUC showed good bioavailability, which was approximately 188.99 times greater than that of the marketed product. According to the in vitro-in vivo correlation, the ex vivo (in vitro) data can represent physiological conditions that are exact replicas of those found in vivo. Therefore, the ZV transdermal patches exhibit enhanced drug permeation and good bioavailability for better therapeutic outcomes.