The excretory function of the kidneys can change dramatically due to age or disease. It is therefore important for clinicians to be able to determine a particular patient’s renal function before dosing a renally eliminated drug.
Creatinine is a breakdown product of muscle. The rate of breakdown is usually fairly steady except in situations of extreme stress or fasting.
Serum creatinine is nearly 100% cleared via the kidneys and as such, it’s clearance can serve as a measurement of the Glomerular Filtration Rate (GFR).
Estimating creatinine clearances is typically performed in one of three ways: