Dermatopharmacokinetic and pharmacodynamic evaluation of a novel nanostructured formulation containing capsaicinoids for treating neuropathic pain

The in vivo skin penetration by dermal microdialysis and the pharmacological efficacy of a chitosan hydrogel containing capsaicinoids-loaded nanocapsules (CHNCcaps) was evaluated in this study. Such gel has previously been proven to control capsaicinoids release and decrease the drugs side effects in humans. The nanocapsules containing capsaicinoids had an average size around 150 nm, with a low polydispersity index, positive zeta potential, and high encapsulation efficiency of the drugs. The CHNC caps showed intact nanocapsules, a slightly acid pH value, and a pseudoplastic behavior suitable for topical application. Microdialysis experiments showed a 1.6-fold increase in the concentration of capsaicinoids in the dermis (after 12 h of its application) when CHNCCaps was administered compared to a chitosan hydrogel containing capsaicinoids in hydroethanolic solution (CHETcaps) and the commercial cream. The CHNC caps showed antiallodynic and antihyperalgesic effects from 6 h to 96 h after treatment initiation, whereas CHET caps and the commercial cream showed antiallodynic and antihyperalgesic effects only at 48 h and 96 h after treatment initiation, respectively. CHNC caps and the commercial cream maintained antihyperalgesic activity for 6 days after treatment interruption. For mechanical allodynia, the antinociceptive effect was maintained for 48 h after treatment interruption only with CHNCCaps. In conclusion, CHNC caps is a promising formulation for treating peripheral neuropathic pain.

Automated summary

The study found that the chitosan hydrogel containing capsaicinoids-loaded nanocapsules (CHNC caps) demonstrated good skin penetration and pharmacological efficacy for treating peripheral neuropathic pain. This formulation showed superior performance compared to other tested options, with sustained antiallodynic and antihyperalgesic effects.