Method: The following formulations were evaluated: unilamellar liposomal 3% mepivacaine (Mepi-LUV), multilamellar liposomal 3% mepivacaine (Mepi-MLV) and 2% mepivacaine with 1:100,000 epinephrine (Mepi-Epi). 30 rats (10/group) received 0.1mL of mepivacaine formulations as IONB in the right side and the respective control at the left side. 48 rats (8/group) received 0.1mL of mepivacaine formulations and the controls in the inflamed right hind paw (submitted to surgical wound and suture). Anesthesia parameters were evaluated by upper lip pinching (IONB) and force application by von Frey anesthesiometer (SISW). Data were submitted to Log-Rank, Kruskal-Wallis and Student-Newman-Keuls tests (α=5%).
Result: Mepi-Epi provided higher success and duration of anesthesia (p<0.05) in both inflamed (SISW) and non-inflamed tissues (IONB). IONB x SISW: All formulations showed lower anesthetic success in the SISW; Mepi-LUV showed lower duration in inflamed tissues.
Table. Success (%) and duration (median and interquartile range, in minutes) of anesthesia.
|
IONB |
SISW |
||||
|
Mepi-Epi |
Mepi-MLV |
Mepi-LUV |
Mepi-Epi |
Mepi-MLV |
Mepi-LUV |
Anesthesia duration (min) |
107.5±55 |
52.5±23.75 |
60±52.5 |
62.5±28.75 |
40±32.5 |
35±22.5 |
Anesthesia success (%) |
||||||
At 40min |
100 |
90 |
70 |
88 |
50 |
50 |
At 90min |
70 |
10 |
30 |
25 |
0 |
0 |
Conclusion: The encapsulation of mepivacaine in unilamellar and mutilamellar liposomes is less potent to improve mepivacaine efficacy than epinephrine in both inflamed and non-inflamed tissues .