• E V Hersh, M Maniar, M Green, and S A Cooper.
• University of Pennsylvania School of Dental Medicine, Department of Oral Surgery and Pharmacology, Philadelphia 19104-6003.
• Anesth Prog. 1992 Jan 1; 39 (6): 197-200.

AbstractThe Lipospheres Bupivacaine Delivery System (bupivacaine-lipospheres) is a novel sustained-release local anesthetic preparation that has recently been made available for research purposes. This investigation compared the local anesthetic efficacy and safety of 2% bupivacaine-lipospheres, 0.5% bupivacaine plus 1:200,000 epinephrine, lipospheres plain, and physiologic saline following subcutaneous tail injection in the rat. A modified tail-flick paradigm was used to assess local anesthetic efficacy. Animals treated with 2% bupivacaine-lipospheres or 0.5% bupivacaine with epinephrine displayed significant antinociception (P < 0.05) compared to saline or lipospheres plain with 5 min of injection. Bupivacaine with epinephrine had an anesthetic duration of 30 min, whereas 2% bupivacaine-lipospheres had a duration of 3 hr. The local anesthetic blockade produced by both active solutions was completely reversible. All animals gained weight normally during the 1-wk course of the study, and there were no signs of local tissue toxicity at the injection sites. We conclude that 2% bupivacaine-lipospheres is a safe and efficacious local anesthetic preparation in this particular animal model. It possesses an onset of action that is a rapid as 0.5% bupivacaine with 1:200,000 epinephrine, and a duration that is six times longer.

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