FIG. 1

Renal clearance and hepatic biotransformation are two possible mechanisms of drug clearance. When a drug undergoes renal clearance, a significant fraction of the dose is recovered in the urine in unchanged form. When a drug undergoes hepatic clearance, liver enzyme systems change the molecular structure of the parent compound. The metabolites produced by hepatic biotransformation often appear in the systemic circulation and are excreted by the kidney (dashed line), but this does not imply renal clearance of the parent drug.

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published 2000