The Poison Review

Intravenous Lipid Emulsion Sequesters Amiodarone in Plasma and Eliminates Its Hypotensive Action in Pigs. Niiya T et al. Ann Emerg Med October 2010;56:402-408.

Abstract

Multiple animal studies and limited clinical experience have suggested that administering IV lipid emulsion has a beneficial effect on outcomes in acute overdose of lipophilic drugs, including bupivacaine, propranolol, verapamil, clomipramine, bupropion, and amitriptyline. The exact mechanism responsible for this effect has not been fully determined. Does the lipid infusion provide a “sink” that sequesters fat-soluble drugs? Or do the lipids primarily provide fuel for the myocardium and improve cardiac function?

The main objective of this animal study was to determine how extensively IV-administered amiodarone was sequestered by an IV infusion of lipid emulsion.  Twenty pigs were anesthetized and instrumented, then given a bolus of either lipid emulsion (ClinOleic) or Ringer’s Lactate, followed by a continuous infusion of same plus IV amiodarone. Blood samples were drawn at 5, 10, and 20 minutes after initiation of amiodarone.

The authors found that in all samples the plasma of the lipid group contained significantly more amiodarone than that of the control group.  In addition, lower concentrations of amiodarone were found in the lipid-poor aqueous fractions of the lipid group samples compared to controls.  The authors conclude that “the lipid soluble amiodarone was sequestered to a great extent by the intravenously administered lipid emulsion”. Their findings support the “lipid sink” theory explaining the beneficial effects of lipid emulsion therapy.

Interestingly, all animals in the lipid group developed mottled red skin.  The two animals with the most extensive skin changes also became hypoxemic.  This finding has not been reported before. (Note that ClinOleic is a different preparation from Intralipid, the emulsion used in most previously published animal and clinical studies.)  The authors hypothesize that this may have something to do with prostaglandins.