Design of Liposomal Lidocaine/Cannabidiol Fixed Combinations for Local Neuropathic Pain Treatment

The administration of drug fixed combinations by nanocarriers is a new attractive approach since it can allow improvements in both the skin penetration of cargo compounds and their synergistic effects. The cutaneous administration of lidocaine (LD) and cannabidiol (CBD) combination can be useful for the local treatment of neuropathic pain. In fact, these drugs might exert a complementary effect on pain acting on sodium and calcium channels. In this study, the feasibility to deliver this combination in the deeper layers of the skin using deformable liposomes was studied. Based on a study of the drug affinity for lipid components performed by DSC, CBD was loaded in the lipid bilayer for limiting the leakage, while LD was loaded in the inner core by a pH gradient method (G-liposomes) or after previous encapsulation in micelle (DiMiL). The effect of the presence of Tween 80 in the liposome membrane was also evaluated. DiMiL increased both the skin permeation and the retention in the dermis of CBD and LD with respect to G-liposomes (R_24dermis: 11.52 ± 2.4 against 4.51 ± 0.8 µg/cm² for CBD; 19.6 ± 2.9 against 3.2 ± 0.1 µg/cm² for LD). Moreover, both DiMiL and G-liposomes were more efficient than control formulations carrying free drugs in improving drug skin permeation. Interestingly, in the presence of a drug exerting a fluidizing effect such as CBD, the removal of Tween 80 from the composition led to an improved control of drug release and a higher extent of drug retention in the dermis layer.