In Vitro Characterization of Cannabidiol As a Possible Adjuvant for Long-Lasting Local Anesthesia

BACKGROUND: Cannabidiol (CBD) inhibits voltage-gated sodium channels (Na v ). CBD is highly lipophilic and exhibits slow binding kinetics on Na v s, a property that may enable CBD to enhance and prolong regional anesthesia. Here we explored the effects of CBD on lidocaine-induced Na v -inhibition and neurotoxicity. METHODS: Patch clamp recordings were performed on tetrodotoxin (TTX)-sensitive Na v s and the TTX-resistant Na v 1.8 in ND7/23 cells or murine dorsal root ganglion neurons (DRG). Cytotoxicity was analyzed using flow cytometry. RESULTS: CBD induced a potent tonic inhibition of sodium currents with slow onset and offset kinetics. Na v 1.8 exhibited a higher sensitivity to tonic block (IC 50 1.4 µM) as compared to TTX-sensitive sodium channels (IC 50 2.9 µM). Similar to local anesthetics, CBD also induced a shift of the steady-state inactivation and a modest use-dependent block at 10 Hz. In contrast to local anesthetics, inhibition of Na v s by CBD is pH-independent. The co-application of CBD and lidocaine resulted in an additive tonic block of sodium currents in ND7/23 cells, but not in DRG neurons. While only high concentrations of CBD induced cytotoxicity, it potentiated lidocaine-induced cytotoxicity. CONCLUSIONS: CBD demonstrates promising characteristics as a long-lasting local anesthetic, or as an adjunct to local anesthetics used for regional or topical anesthesia.