Characteristics and Vasodilating Effects of Liposomal PGE1 Preparations.

Alprostadil (PGE1) shows potent vasodilating effect and anti-platelet effect and its clinical usefulness has been confirmed. But it is known that plasma half life of PGE1 is very short because it is easily metabolized very rapidly mainly in lung. It is considered that avoiding the rapid enzymatic attack is important point to make a effective formulation of PGE1. We studied two liposomal formulations of PGE1, liposome with pH gradient and liposome composed of hydrogenated egg phophatidylcholine (H-EPC). Both liposomal preparations showed higher plasma concentration of PGE1 than PGE1 solution when these preparations were administered intravenously to rats. Pharmacological effect of liposomal preparations was also stronger than that of PGE1 solution. The effect was in proportion to plasma concentration of PGE1. Liposomal PGE1 with pH gradient was presumed to be stable for 2 years below 10° after lyophilization. It is concluded that these liposomal preparations of PGE1 could be promising candidates for human use.