An evaluation of the analgesic effect of AnestaGel™ on mechanical allodynia in a rat model of postoperative incisional pain

Jacob Hutchins,1 William Taylor2 1Department of Anesthesiology, University of Minnesota, Minneapolis, MN, USA; 2InSitu Biologics, LLC, St Paul, MN, USA Purpose: Sustained release hydrogel with bupivacaine (AnestaGel™) is a novel formulation of extended release bupivacaine in a biohydrogel Matrix™. We sought to compare the analgesic effects via mechanical allodynia, the pharmacokinetic characteristics via serum blood levels, and the local tissue effects via pathology, following injection of either sustained release hydrogel with bupivacaine, liposome bupivacaine, or hydrogel only (negative control group). Materials and methods: Ninety rats (30 in each group) were randomized to receive a sciatic nerve block injection of either sustained release hydrogel with bupivacaine, liposome bupivacaine (Exparel®), or a biohydrogel matrix. The total force generated was obtained at varying time points. Pathologic analysis was undertaken on days 5 and 42 of the study. Six additional rats (two in each group) were randomized to receive a sciatic nerve block injection of either sustained release hydrogel with bupivacaine, liposome bupivacaine, or bupivacaine and pharmacokinetic data were obtained for up to 120 hours. Results: The sustained release hydrogel with bupivacaine group had significantly better response to mechanical allodynia compared to the other two groups. The pathology showed no significant adverse events at 42 days in any group. Finally, bupivacaine was present longer in the serum of sustained release hydrogel with bupivacaine group than the other two groups. Conclusion: The sustained release hydrogel with bupivacaine achieved longer lasting analgesia with no significant findings on pathology at 42 days when compared to both positive and negative controls. Keywords: mechanical allodynia, local anesthetics, extended release, nerve bloc