The Effect of Lipid Emulsion on Pharmacokinetics of Bupivacaine in Rats: Long-Chain Triglyceride Versus Long- and Medium-Chain Triglyceride.

BACKGROUND: Lipid infusions have been proposed to treat local anesthetic-induced cardiac toxicity. This study compared the effects of long-chain triglyceride (LCT) emulsions with those of long- and medium-chain triglyceride (LCT/MCT) emulsions on the pharmacokinetics of bupivacaine in a rat model. METHODS: After administration of intravenous infusion of bupivacaine at 2 mg[middle dot]kg-1[middle dot]min-1 for 5 minutes in Sprague-Dawley (SD) rats, either Intralipid 20%, an LCT emulsion (LCT group, n = 6), or Lipovenoes 20%, an LCT/MCT emulsion (LCT/MCT group, n = 6), was infused at 2mg[middle dot]kg-1[middle dot]min-1 for 5 minutes. The concentrations of total plasma bupivacaine and bupivacaine that were not bound by lipid (lipid unbound) were measured by a liquid chromatography-tandem mass spectrometric method. A 2-compartmental analysis was performed to calculate the lipid-bound percentage of bupivacaine and its pharmacokinetics. RESULTS: In the LCT group, the clearance (15 +/- 2 vs 10 +/- 1 mL[middle dot]min-1[middle dot]kg-1, P = .003) was higher; the volume of distribution (0.57 +/- 0.10 vs 0.36 +/- 0.11 L[middle dot]kg-1, P = .007) and K21 (0.0100 +/- 0.0018 vs 0.0070 +/- 0.0020 min-1, P = .021, P' = .032) were larger; and the area under the blood concentration-time curve 0 - t; (605 +/- 82 vs 867 +/- 110 mgL-1[middle dot]min-1, P = .001) and the area under the blood concentration-time curve (0 - [infinity]) (697 +/- 111 vs 991 +/- 121 mgL-1[middle dot]min-1, P = .001) were less, when compared with the LCT/MCT group. CONCLUSIONS: LCT emulsions are more effective than LCT/MCT emulsions in the metabolism of bupivacaine through demonstration of a superior pharmacokinetic profile. (C) 2016 International Anesthesia Research Society

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