Medical auxiliary agent comprises at least a liquid semifluorinated alkane (I), as carrier for at least an active agent, where the active ingredient is colloid- to molecularly-dispersed, and dissolved in the liquid for the passage into the alveolar membrane and transport into the blood stream with a particle size of 1-0.1 nm, in homogeneous phase. Medical auxiliary agent comprises at least a liquid semifluorinated alkane of formula (RFRH) (I), as carrier for at least an active agent, where the active ingredient is colloid- to molecularly-dispersed, and dissolved in the liquid for the passage into alveolar membrane and transport into the blood stream with a particle size of 1-0.1 nm, in homogeneous phase. RF : perfluoroalkyl group； and RH : saturated hydrocarbon group. ACTIVITY : Respiratory-Gen.； CNS-Gen. MECHANISM OF ACTION : None given.
