This blinded crossover study evaluated the efficacy and pain sensitivity evoked by a previously reported liposome-encapsulated mepivacaine formulation (Araujo et al., 2004). Thirty healthy volunteers received an intraoral injection (1.8 mL), at four different sessions, of the following formulations: 2% mepivacaine with 1:100,000 epinephrine (MVC(2%EPI)), 3% mepivacaine (MVC(3%)), and 2 and 3% liposome-encapsulated mepivacaine (MVC(2%LUV) and MVC(3%LUV)). Latency period and duration of anesthesia were assessed by an electrical pulp tester and injection discomfort by a visual analog scale (VAS). Data were analyzed with Tukey-Kramer and Friedman tests (P < 0.05). No significant difference was found regarding latency period (in minutes) among the formulations (P > 0.05). The duration of anesthesia after the injection of MVC(3%LUV) was higher than the one obtained after the infiltration of MVC(2%LUV) and of MVC(3%) (P < 0.05). However, the duration of anesthesia obtained with MVC(3%) did not differ from the one obtained with MVC(2%LUV) (P > 0.05). MVC(3%LUV) showed lower VAS median values than MVC(2%EPI) (P < 0.05), and there were no significant differences among the others formulations. Liposome-encapsulated 3% mepivacaine showed longer duration of anesthesia, in comparison to the commercial formulation of MVC(3%). MVC(2%LUV) was able to produce a similar duration of anesthesia as the 3% commercial formulation, despite the 50% decrease in the anesthetic concentration. Thus, the encapsulation of mepivacaine increased the duration of anesthesia and reduced the injection discomfort caused by vasoconstrictor-associated formulations in healthy volunteers.
Trial registration: ClinicalTrials.gov NCT01032798.