Anesthetic efficacy of liposomal articaine in rats

Liposome encapsulation has been found to enhance the clinical efficacy of local anesthetics. This study evaluated the anesthetic efficacy of two liposomal formulations of articaine (3% and 4%) by means of two animal models: infraorbital nerve block (IONB) and inferior alveolar nerve block (IANB) in rats. For each experiment, 48 animals were divided in 6 groups (n=8), which received the injection of one of the following formulations, in the right side: Group 1: 4% articaine with 1:100,000 epinephrine; Group 2: 4% liposomal articaine; Group 3: 3% liposomal articaine; Group 4: 4% articaine; Group 5: 3% articaine and Group 6: 4mM liposome. The left side received NaCl 0.9% (control). For the IONB, 0.1 mL of the tested formulation was injected near the rat infraorbital foramen. The duration of soft tissue anesthesia was evaluated by pinching the upper lip, every 5 minutes, until the first sign of aversive response was observed. For the IANB, 0.2 mL of the tested formulations was injected near the rat mandible foramen and the parameters onset and duration of pulpal anesthesia were evaluated by means of an electrical pulp tester. Data were submitted to ANOVA test and significance level was set at 5%. Concerning soft tissue anesthesia, groups 1, 2 and 3 showed similar duration (p>0.05) which were longer than that of the groups 4 and 5 (p<0.05). Group 1 showed the shortest onset of pulpal anesthesia (p<0.05) and there was no difference among groups 2, 3, 4 and 5 (p>0.05). Group 1 promoted longer duration of pulpal anesthesia (p<0.05) followed by groups 2 and 3. Concerning duration of pulpal anesthesia, no significant difference was found between groups 2 and 3 and groups 4 and 5 (p>0.05). Liposome encapsulation prolonged anesthetic effects of articaine when compared to plain solution. However, the epinephrine-containing solution showed longer pulpal anesthesia duration than liposomal formulations. (AU)