Rate of release and retentivity of prostaglandin E1 in lipid emulsion.

The rates of release of prostaglandin E1 (PGE1) from lipid particles into aqueous solution were obtained by the dialysis method, for parenteral lipid emulsion (Lipo-PGE1) diluted 10-times with buffered solutions of various pH. The findings, which were the rates of release of PGE1, were used to calculate the amount of PGE1 distributed in lipid particles when Lipo-PGE1, diluted 100-times with various pH levels of the buffered solution, was administered by intravenous drip infusion. More than 90% of PGE1 was retained in the lipid particles and intravenously infused when transfusion fluid pH was less than 5.5 and 2 ml of Lipo-PGE1 and 198 ml of transfusion fluid had been mixed and were administered over 2 h. Results from simulation showed that half of the PGE1 was retained in lipid particles and was infused, if Lipo-PGE1 was diluted 100-times with pH 8 transfusion fluid. Though PGE1 was sparingly soluble in an aqueous solution, these findings demonstrated that a significant amount of PGE1 was retained in lipid particles. Thus, this dosage form is expected to be highly effective for a drug delivery of PGE1 in clinical treatment.