Comparative study of transdermal lidocaine delivery using different eutectic mixtures

Transdermal delivery can provide needle-free drug administration and avoid first-pass drug degradation in the liver, thus improving the quality of life for patients. Recently, eutectic mixtures have attracted considerable attention as components of transdermal drug delivery systems. In the present study, lidocaine was selected as a model drug, and dose-dependent transdermal delivery was evaluated using mixtures of lidocaine and menthol with different lidocaine weight fractions. The results indicated that all the eutectic mixtures exhibited enhanced skin penetration, and thus a comparative study was conducted by evaluating skin penetration in mole unit rather than mass unit. Three different lidocaine-based eutectic mixtures were prepared by adding ibuprofen, prilocaine, or menthol. Skin penetration results in the mole unit revealed that menthol was the most effective counter agent, producing eutectic mixtures with a high skin penetration effect. Mathematic analysis of the time-course cumulative amount of penetrated lidocaine in the mole unit suggested that although menthol did not enhance the diffusion of lidocaine in the skin, it enhanced the partition of lidocaine from the eutectic mixture to the outermost layer of the skin. This finding is helpful in the preparation of effective eutectic mixtures for transdermal drug delivery.