Application of quality by design principles in the development and evaluation of semisolid drug carrier systems for the transdermal delivery of lidocaine

The aim of this work was the formulation and comparison of different drug carrier systems for the transdermal delivery of lidocaine. Quality target product profile and quality attributes were identified, and an initial risk assessment was made according to the Quality by Design methodology. The critical quality attributes influencing the quality and efficacy of the final drug formulation were then defined in order to select the control points. Four formulation types, each containing 5% lidocaine were compared: conventional hydrogel, oleogel, lyotropic liquid crystal and nanostructured lipid carrier. Microscopic analysis, particle size and zeta potential measurements, Fourier transform infrared spectroscopy and Raman spectroscopy were performed to characterize the critical parameters in case of the different vehicles. Membrane diffusion and penetration studies were completed as well for each formulation in vitro and ex vivo, followed by measurements on skin hydration and transepidermal water loss in vivo. Our results lead us to the conclusion that the nanostructured lipid carrier is the most promising vehicle for the topical delivery of lidocaine. It showed the best penetration properties through heat separated epidermis and the highest moisturizing effect which are the most critical parameters based on the Quality by Design initial risk assessment and evaluation.