Anesthetic efficacy of uni and multilamelar liposomal articaine formulations in block of infraorbital and inferior alveolar nerve and in subcutaneous infiltration in surgical wound, in rats

This study assessed the anesthesic efficacy of the following formulations: 4% articaine encapsulated in multilamellar liposomes (Arti-MLV), 4% articaine encapsulated in unilamellar liposomes (Arti-LUV) and 4% articaine with 1:100,000 epinephrine (Arti-Epi), in three animal models: infraorbital nerve block (IONB), subcutaneous infiltration in surgical wound (SISW) and inferior alveolar nerve block (IANB). For IONB, 24 rats (8/group) received 0.1 mL of the anesthetic formulations near the right infraorbital foramen. The duration of anesthesia was assessed by upper lip pinching every 5 minutes. For SISW, 36 animals (6/group) received 0.1 mL of the anesthesic formulations 24 hours after a surgical wound (incision and suture) was performed in the plantar region of the right hind paw. Paw anesthesia was assessed by force application at the side of the wound with electronic von Frey anesthesiometer. For IANB, 45 rats (15/group) received 0.2 mL of the anesthetic formulations near the right mandibular foramen. The success, onset and duration of pulpal anesthesia were assessed by electric stimulus. 0.9% NaCl solution, multilamellar liposomal suspension and unilamellar liposomal suspension were used as negative controls in the three models studied. Data were submitted to ANOVA, Kruskal-Wallis, Student-Newman-Keuls, Log-Rank, and Fisher's exact tests (5% significance level). For IONB no differences in duration and anesthesic success (p>0.05) were observed between Arti-Epi and Arti-MLV; Arti-Epi presented higher anesthesia duration than Arti-LUV (p<0.05). Arti-LUV provided lower (p<0.05) anesthesia success than other formulations. For SISW, Arti-Epi provided higher success and longer anesthesia duration than the other formulations (p<0.05). For BNAI no differences among the formulations were observed in relation to onset, success and anesthesia duration (p>0.05). In conclusion, the articaine liposomal formulations presented anesthetic efficacy equivalent to that showed by the solution with epinephrine and could be an option for pulpal (IANB) and soft tissue anesthesia in non-inflamed tissues (IONB - only the multilamellar liposome formulation). However, the solution with epinephrine was more potent to improve anesthetic success and duration in tissues with hipernociception (AU)