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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

Glomerular filtration rate (GFR)

• Glomerular filtration rate is measured by using a drug that is eliminated by

filtration only (i.e., the drug is neither reabsorbed nor secreted).

• Examples of such drugs are inulin and creatinine.

• Therefore, the clearance of inulin is equal to the GFR, which is equal to 125–130

mL/min.

I. If the drug is filtered but not secreted or reabsorbed, the renal clearance will be about

120 ml/min in normal subjects.

II. If the renal clearance is less than 120 ml/min then we can assume that at least two

processes are in operation, glomerular filtration and tubular reabsorption.

III. If the renal clearance is greater than 120 ml/min then tubular secretion must be

contributing to the elimination process.

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