Multivesicular liposomal bupivacaine at the sciatic nerve

Clinical translation of sustained release formulations for local anesthetics has been limited by adverse tissue reaction. Exparel (TM) (DepoFoam bupivacaine) is a new liposomal local anesthetic formulation whose biocompatibility near nerve tissue is not well characterized. Exparel (TM) injection caused sciatic nerve blockade in rats lasting 240 min compared to 120 min for 0.5% (w/v) bupivacaine HCl and 210 min for 1.31% (w/v) bupivacaine HCl (same bupivacaine content as Exparel (TM)). On histologic sections four days after injection, median inflammation scores in the Exparel (TM) group (2.5 of 4) were slightly higher than in groups treated with bupivacaine solutions (score 2). Myotoxicity scores in the Exparel (TM) group (2.5 of 6) were similar to in the 0.5% (w/v) bupivacaine HCI group (3), but significantly less than in the 1.31% (w/v) bupivacaine HCl group (5). After two weeks, inflammation from Exparel (TM) (score 2 of 6) was greater than from 0.5% (w/v) bupivacaine HCl (1) and similar to that from 131% (w/v) bupivacaine HCl (1). Myotoxicity in all three groups was not statistically significantly different. No neurotoxicity was detected in any group. Tissue reaction to Exparel (TM) was similar to that of 0.5% (w/v) bupivacaine HCl. Surveillance for local tissue injury will be important during future clinical evaluation. (C) 2014 Elsevier Ltd. All rights reserved.