Topical delivery of Lidocaine using spicules for local anesthesia

Topical anesthesia offers a painless alternative to injections but is limited by the low skin permeability of local anesthetics through the stratum corneum, leading to a slow onset. In this study, we introduce a novel spicule-assisted topical delivery system using Sponge Haliclona sp. spicules (SHS) combined with Carbomer gel to enhance the transdermal absorption of lidocaine hydrochloride (LH). SHS act as dispersed microneedles, creating numerous microchannels that significantly improve skin permeability. In vitro, SHS increased total skin absorption of LH nearly tenfold (78.45 ± 6.96%) and accelerated drug penetration into deeper skin layers (97.5% in dermis and receptor compartments). In vivo, SHS-LH treatment achieved a maximum anesthetic effect within 10 min, markedly faster and stronger than conventional topical application. A pilot clinical trial confirmed that the SHS-Carbomer gel system halved the onset time of lidocaine and significantly prolonged its anesthetic effect. These findings demonstrate that the SHS-based dispersed microneedle system provides a rapid, safe, and needle-free alternative for local anesthesia, offering a substantial improvement over conventional topical formulations.