Which route is described as exhalation (pulmonary) in drug excretion?

Which route is described as exhalation (pulmonary) in drug excretion?

• A. Urine (renal)
• B. Stool (hepatic, biliary)
• C. Exhalation (pulmonary)
• D. Absorption (GI)

Answer: (C)

Pulmonary excretion occurs when a drug is volatile enough to transfer from blood into the alveolar air and be exhaled. This route depends on the drug’s volatility and its blood–gas partition coefficient: drugs with low blood solubility and high volatility cross into the breath more readily and are eliminated via exhalation. This is why volatile anesthetics and certain small, volatile compounds can be exhaled, making pulmonary excretion the route described as exhalation. In contrast, most drugs are eliminated mainly by the kidneys (urine) or via biliary/fecal routes, with absorption through the GI tract not serving as an excretion pathway.

Pulmonary excretion occurs when a drug is volatile enough to transfer from blood into the alveolar air and be exhaled. This route depends on the drug’s volatility and its blood–gas partition coefficient: drugs with low blood solubility and high volatility cross into the breath more readily and are eliminated via exhalation. This is why volatile anesthetics and certain small, volatile compounds can be exhaled, making pulmonary excretion the route described as exhalation. In contrast, most drugs are eliminated mainly by the kidneys (urine) or via biliary/fecal routes, with absorption through the GI tract not serving as an excretion pathway.