Abstract: A method for oral administration of an active principle includes the steps of incorporating an active principle in multilamellar vesicles having a diameter of between 0.1 and 25 &mgr;m, and a lamellar liquid-crystal internal structure formed, from the center to the periphery of the vesicles, of a stack of concentric bilayers based on amphiphilic agents alternating with layers of water, aqueous solution or solution of a polar liquid, and orally administering a composition containing the active principle incorporated within the vesicles.

Abstract: The invention relates to the use of multilamellar vesicles having a lamellar liquid-crystal internal structure made up of amphiphilic agent-based concentric bilayers alternated with layers of water, aqueous solution or a solution of a polar liquid, from the center to the periphery of the vesicles, and in which at least one active agent is incorporated, for producing a pharmaceutical composition for oral administration. Said vesicles act as vectors of the active agent and enable said active agent to cross the gastro-intestinal barrier more easily. The vesicles also protect the active agent from decomposition, especially decomposition by the enzymes present in the gastro-intestinal environment. The invention also relates to novel compositions for oral administration, especially compositions containing heparin, incorporated in vesicles such as those described above.