Liposomal binding of imipramine in human red cell/albumin solution with simulated plasmapharesis

There has been much recent interest in the use of intravenous lipid based products inthe treatment of tricyclic ntidepressant toxicity. High affinity liposomal carriers have been designed which may be more effective binders of tricyclic antidepressant than intravenous lipid emulsion in the setting of intoxication. The uniformity and size of the liposomes opens the theoretical potential for extracorporeal removal of drug once bound. Imipramine was added to a suspension of human red blood cells and albumin. Liposomes of known high affinity for tricyclics were then added to this suspension. It was hypothesized that the imipramine would be bound to liposomes, which could then be filtered off in a staged process, first using a commercially available plasmapharesis filter and then through a 100nm filter. tatistically significant reductions in imipramine concentration were seen in the final components post filtration, both red cell rich (median, 24% original level, IQR 9-43%) and "pharesate", liposomes filtered off (median 23%, IQR 9-37%) . We have demonstrated significant experimental binding of imipramine to liposomes ina human albumin/red blood cell uspension, and have removed liposomes from thissuspension after drug sequestration. Further work is planned to investigate the effect ofliposomes in TCA toxicity in an animal model.