Other excretion

Excretion with the bile (and thereby with feces), sweat, exhaled air, saliva, and breast milk play a much smaller role compared to urine. An exception is the excretion of volatile anesthetics with exhaled air. The particular importance of the excretion via breast milk lies in the toxic effects of some drugs on the breastfeeding infant. Note that substance-specific portions of orally administered drugs are removed with feces without entering the circulation. This is due to their incomplete absorption from the gastrointestinal tract. In contrast, some drugs undergo multiple cycles of absorption and excretion with the bile (enterohepatic circulation).