Topical delivery of Lidocaine using spicules for local anesthesia

Abstract Local anesthesia has been extensively utilized in medical and surgical fields. We screened and optimized the application formula of lidocaine hydrochloride (LH). We utilized the combination of Sponge Haliclona sp. Spicules (SHS) with Carbomer gel to overcome the skin barrier and increase the skin absorption of lidocaine hydrochloride in vitro and in vivo. We first investigated the skin permeation and deposition behavior of LH with or without SHS in vitro. SHS can dramatically (p < 0.001) increase the total skin absorption of LH (78.45 ± 6.96%) compared to the control group (passive penetration, 8.20 ± 1.60%). We also found most of LH (97.51 ± 0.17%) accumulated in deep skin layers (dermis and receptors), while only 35.99 ± 4.80% of LH accumulated there in the control. We next investigated the local anesthetics efficacy of LH with or without SHS using tail-flick latency (TFL) test in rats. SHS resulted in the highest MEP (maximum possible effect) of 5.15 ± 0.82 s at approximately 10 minutes, while the highest MEP of 2.60 ± 0.27 s appeared at around 45 minutes in the control group. Further, we carried out an investigator initiated clinical trial (IIT) to verify the clinical effectiveness of LH with or without SHS. SHS resulted in a significant difference in laser pain scores (4.40 ± 0.55, p<0.05) since 10 minutes post-application of LH cream compared to the control group (5.00 ± 0.00). Therefore, SHS can significantly enhance the skin absorption of lidocaine hydrochloride, effectively shorten the onset time of anesthesia and significantly improve the anesthetic effect of LH in clinical practice.