Excretion

The final stage in metabolism takes place when the drug is changed in to an inactive form or excreted from the body. The kidneys are the most important route of excretion because they eliminate both the pure drug and the metabolism of the parent drug.

During excretion, these two substances are filtered through glomeruli, secreted by the tubules, and either reabsorbed through the tables or directly excreted. Other routes of excretion include the lungs (which exhale gaseous drugs). Feces, saliva, tears, and mother’s milk