The Role of Liposome Composition on the Stabilization of Ancitabine

Abstract

Reduction in the ancitabine hydrolysis rate in an alkaline medium was achieved by liposome encapsulation of stable ancitabine solutions. The degree of success was gauged using stabilization ratios which compare rates of hydrolysis of free and encapsulated ancitabine under identical conditions. Stabilization ratios as high as 22 were observed when the phase transition temperature (PTT) values were 16 to 26°C higher than the storage temperature. Liposomes composed of phospholipids with PTT values below storage temperatures were ineffective. Increased liposome permeability was evidenced by rapid, nearly complete, release of encapsulated ancitabine at temperatures above the PTT. The inclusion of cholesterol in the liposomes reduced the maximum stabilization ratios from 22 to 4.