抄録
Mechanism of drug absorption from micellar solution was studied through use of drugs which exist predominantly in micellar phase. Particular systems chosen were vitamin A acetate and vitamin A alcohol-Polysorbate-80. Contrary to the notion that the only form in which the drug penetrate the membrane is free drug, both vitamins, entrapped almost completely in micelles, were absorbed fairly well, but not as such, form the rat large intenstine. Disappearance of the vitamins from the perfusate proceeded by two phases, the rapid (initial 15 minutes perfusion period) and the slow phase (follwing 60 minutes period). In the former, extent of the absorption of the vitamins were dependent on the initial concentration of surface-active agent, whereas in the latter, no such tendency was observed. It was demonstrated that in the very early stage of absorption, vitamins solubilized in micelles are absorved onto the membrane, which being favored by the surface-active agent and in the slow phase, absorption now becomes rate-limited by the partition or release of the vitamins from adsorbed micelles to the mucosal layer of the membrane. Despite the large effective surface area, disappearance in the slow absorptive phase of the vitamins from the solution circulated through the small intestine was smaller compared with the large intestine.
