Carrier activity of sonicated small liposomes containing melphalan to regional lymph nodes of rats.

Tissue distribution following subcutaneous injection of liposomes containing melphalan (MPL) was studied in rats using 14C-MPL and 3H-phosphatidylcholine. Two types of liposomes, prepared by either a brief or a prolonged sonication, were compared. Brief sonication formed large liposomes of various sizes, while liposomes obtained after a prolonged sonication were small and relatively uniform in size (34 nm in mean diameter). Subcutaneous injection of small liposomes produced a strikingly high and sustained concentration of MPL equivalents in regional lymph nodes. In contrast, most liposomes prepared by a brief sonication appeared to remain at the injection site, and there was only a slight increase in the lymph node concentration of MPL equivalents over the plasma level during the 24-hour experiments.