Excretion Rate & Renal Clearance Calculator
Results:
Excretion Rate: 0 units/min
Renal Clearance (Cl): 0 mL/min
Understanding Excretion Rate Calculation
The excretion rate represents the quantity of a specific substance (such as a drug or metabolic waste product like creatinine) that is removed from the body by the kidneys per unit of time. This is a critical metric in pharmacokinetics and physiology used to assess kidney function and drug dosing.
The Basic Formula
To find the excretion rate, you must multiply the concentration of the substance in the urine by the rate at which urine is being produced. The standard formula is:
- U: Concentration of the substance in the urine (e.g., mg/mL).
- V: Urine flow rate (e.g., mL/min).
Calculating Renal Clearance
Renal clearance describes the volume of plasma that is completely cleared of a substance by the kidneys per unit of time. It relates the excretion rate to the concentration of the substance currently in the blood (plasma):
Where P is the plasma concentration of the substance.
Real-World Example
Imagine a patient with the following lab results for a specific drug:
- Urine Concentration (U): 4 mg/mL
- Urine Flow Rate (V): 1.5 mL/min
- Plasma Concentration (P): 0.2 mg/mL
Step 1: Calculate Excretion Rate
Excretion Rate = 4 mg/mL × 1.5 mL/min = 6 mg/min.
Step 2: Calculate Renal Clearance
Clearance = 6 mg/min ÷ 0.2 mg/mL = 30 mL/min.
In this case, 30 milliliters of plasma are being cleared of the drug every minute.