Removal from the Body

The primary route for drug removal is through the kidneys, which act as filters and reabsorb most of the water and fat-soluble substances in the blood. Therefore, the elimination of fat-soluble psychoactive substances by the kidneys (and intestines) is very inefficient. Instead, through drug metabolism they are transformed into water-soluble substances. Drugs can also be excreted in breath, sweat, saliva, the placenta, and a mother’s milk.