the invention concerns liposome vectors , in powder form , of active principles , and more particularly active principles sensitive to digestive and / or plasmatic degradation , such as proteins , and their application as medicine . said liposome vectors of active principles consist of a powder composition essentially constituted of unilamellar liposomes comprising an external lipid phase consisting of class 4 lipids , optionally associated with class 2 substances , class 3 substances and / or class 5 substances and an internal aqueous nucleus consisting of a mixture m of at least two different non - polymerisable gelling agents whereof the gel - sol phase transition is not less than 37 ° c ., g1 being selected among gelatines and carrageenans and g2 being selected among carrageenans with properties different from the carrageenans selected for g1 , and celluloses , which liposomes have a diameter ranging between 20 nm and 1 mm , preferably between 20 nm and 500 nm ; said composition having the form of particulate units with an average particle diameter between 10 mm and 1000 mm , formed by one or several of said liposomes , enclosed in a sheath selected in the group consisting of a dehydrated thermoreversible aqueous gel identical to said internal nucleus aqueous gel , dextrins or a mixture thereof , such that they contain , on an average , 10 to 10 liposomes per gram of powder ; and at least an active principle contained , as the case may be , either in the gelled internal nucleus or in the external lipid phase .