Formulation and In-Vitro Performance of Liposome Powder Aerosols

The formulation of lyophilized liposome cakes, micronization of the cake, aerosolization using a dry powder inhaler, and the in vitro distribution of such powders upon aerosolization in a silicone elastomer throat attached to an Andersen cascade impactor are reported. Two liposome compositions consisting of phosphatidylcholine/phosphatidylglycerol and phosphatidylcholine/cholesterol are examined. Fluorescent marker molecules, 5,6-carboxyfluorescein and N,N'-bis(1-hexlheptyl)-3,4:-9,10-perylene-bis (dicarboximide), are used to monitor directly the distribution of liposomal lipid upon aerosolization. The results demonstrate that milled micronized liposome powders can be effectively aerosolized at a fixed flow rate. The de-aggregation and dispersion of the liposome powder is not significantly improved by the addition of spray-dried lactose used as carrier powder