Methods: In this double-blinded crossover study forty healthy volunteers received 100mg of the following topical anesthetics (randomly applied, one in each side, in each session – latin square): Liposome-encapsulated 4% lidocaine gel (LELG), 5% lidocaine (XYLO – Xylocaine ointment®, AstraZeneca), euthetic mixture of 2.5% lidocaine and 2.5% prilocaine (EMLA, EMLA cream®, AstraZeneca), and liposome gel without anesthetic (LGCO - control) on the palatal mucosa of both maxillary canines, for 2 minutes, in two sessions. After this period a 30-G needle was inserted and a 1/6 cartridge of 2% lidocaine with 1:100,000 epinephrine (LE) was injected. Pain associated with the needle insertion and LE injection was rated on two separated visual analogue scales (VAS). The results were compared by Friedman and Wilcoxon sign-ranked tests (α=5%).
Results: VAS values (median ± interquartile range, in cm) for LELG, XYLO, EMLA and LGCO, respectively: Needle Insertion: 0.15±0.24, 0.19±0.21, 0.15±0.29, and 0.22±0.24; LE injection: 0.12±0.23, 0.15±0.21, 0.14±0.19, and 0.22±0.23. There were no significant differences (p>0.05) regarding VAS values (needle insertion and LE injection) among the groups except for LELG that presented lower (p<0.05) VAS values (needle insertion and LE injection) than LGCO (control).
Conclusion: Liposome-encapsulated 4% lidocaine gel reduced pain during needle insertion and local anesthetic injection in comparison to the control gel and was equivalent to 5% lidocaine ointment (Xylocaine) and the euthetic mixture of lidocaine and prilocaine (EMLA). Supported by FAPESP 2010/20382-7 and 2006/00121-9.