PROBLEM TO BE SOLVED: To provide a method for using an oxygen-containing gas source.SOLUTION: The present invention is a method for using an oxygen-containing gas source which is used for preparing a pharmaceutical composition for improving blood brain barrier permeability in which a gas source contains at least 20 wt.% of oxygen. The oxygen-containing gas source can improve blood brain barrier permeability, is easily operated, does not require an expensive device, can quickly recover non-permeability of the blood brain barrier after a compound is transmitted to a cerebrum, and can protect cerebrum environment not to be interfered by external substances, so that an oxygen-containing gas source of the present invention can be used for preparing a pharmaceutical composition for improving blood brain barrier permeability.SELECTED DRAWING: Figure 9A【課題】酸素含有気体源の使用方法を提供することにある。【解決手段】本発明は、血液脳関門浸透性向上用の医薬組成物の調製に用いられ、気体源が少なくとも20重量%の酸素を含む酸素含有気体源の使用方法である。酸素含有気体源は、血液脳関門浸透性を向上させることができ、操作しやすく高価な機器をいらず、化合物が大脳に伝送された後で血液脳関門の非浸透性が快速に回復できて、外界物質に干渉されないように大脳の環境を保護できるので、本発明の酸素含有気体源を血液脳関門浸透性向上用の医薬組成物の調製に用いることができる。【選択図】図9A