Effects of Topical Administration of a Nanoemulgel of Capsaicin and Lidocaine in Models of Advanced Diabetic Neuropathy.
Diabetic Neuropathy; Hypoalgesia; Nerve Regeneration; Capsaicin; Lidocaine
Advanced diabetic neuropathy (ADN) is a serious complication of diabetes mellitus (DM), characterized by the loss of protective heat sensitivity (thermal hypoalgesia), which dramatically increases the risk of serious complications. This condition is often associated with decreased epidermal nerve fiber density. This study aims to investigate whether topical application of a capsaicin and lidocaine nanoemulsifier can restore protective sensitivity and promote nerve regeneration in rat models of ADN. Twenty-one male Wistar rats were divided into three groups of seven animals: negative control (treated with excipients), positive control (treated with commercial capsaicin at 0.075%), and experimental group (treated with the nanoemulsifier). Protective sensitivity was assessed quantitatively using the hot plate test at 47°C. Analysis of nerve regeneration by immunohistochemistry (PGP9.5 marker) is ongoing. In the behavioral tests (hot plate), in the intragroup analysis (pre-treatment vs. post-treatment), neither treatment reversed hypoalgesia. However, the commercial capsaicin cream worsened the condition (p=0.0313), while the nanoemulgel (p=0.3125) and the excipients (p=1) did not. The intergroup analysis confirmed a significant difference between the nanoemulgel and the commercial cream (p=0.0070), and no significant difference between the nanoemulgel and the excipients (p=0.0313). The partial results suggest that, although the new nanoemulgel was unable to restore sensation, it demonstrated a superior safety profile to the commercial treatment, as it did not worsen thermal hypoalgesia. A complete conclusion about the efficacy of the nanoemulgel will depend on the results of the intraepidermal nerve fiber density analysis, which will complement the behavioral data.