Drug metabolism

Japanese: 薬物代謝 - やくぶつたいしゃ（英語表記）drug metabolism

Drugs are primarily taken for the purpose of treating or preventing diseases, but the body that receives the drugs regards them as foreign substances and tries to excrete them from the body as quickly as possible. Most drugs are excreted in urine, but some are also excreted in feces, lungs, skin, etc. On the other hand, if a drug has high lipid solubility, it is reabsorbed in the renal tubules, so very little of the drug is excreted in the urine in the form in which it was administered. In this case, highly lipid-soluble drugs are polarized by various enzyme systems in the body into a form that is easily excreted from the kidneys, that is, in the direction of increasing water solubility.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

薬物はおもに疾病の治療や予防の目的で服用されるが，薬物を受け入れる生体側は，薬物を異物とみなし，生体から速やかに排出しようとする。薬物のほとんどは尿中に排出されるが，糞便中や肺や皮膚などからも排出される。一方，薬物が高い脂溶性を有する場合は，腎臓の尿細管で再吸収されるので，尿中には投与した形の薬物としてはほとんど排出されない。この場合，脂溶性の高い薬物は，生体内の種々の酵素系によって腎臓から排出されやすい形，すなわち水溶性が大きくなる方向に極性化される。

出典　株式会社平凡社世界大百科事典第２版について　情報

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