Liposomal Mepivacaine Efficacy In Infraorbital Nerve Block In Rats

Objective: To evaluate the anesthetic efficacy of liposomal mepivacaine with epinephrine in rats. Methods: After light sedation with sodium thiopental 30 rats were divided into 3 groups which received 0.1mL of the following formulations in infraorbital nerve block: 2% liposomal mepivacaine; 2% liposomal mepivacaine with 1:100,000 epinephrine and 2% mepivacaine with 1:100,000 epinephrine. The contralateral side of the maxilla received the same volume of saline (control). Each 5 minutes after the injection both sides of the upper lip were pinched in order to evaluate the anesthetic effectiveness (absence of aversive stimulus). The results were submitted to ANOVA (alpha=5%). Results: The duration of anesthesia in the upper lip (mean ± standard deviation) for each group was: 107.5 ± 25.6 min for 2% liposomal mepivacaine; 124.5 ± 42.6 min for 2% liposomal mepivacaine with 1:100,000 epinephrine and 109.5 ± 47.1 min for 2% mepivacaine with 1:100,000 epinephrine. No differences (p=0.59) were observed among the formulations. Conclusion: liposomal mepivacaine presents similar anesthetic efficacy to mepivacaine with epinephrine in the infraorbital nerve block model in rats. The addition of epinephrine to the liposomal mepivacaine formulation does not improve its anesthetic efficacy. Supported by FAPESP (#2006/00121-9).