What is the clearance of a substance when its concentration in the plasma is 10 mg/dl, its concentration in the urine is 100 mg/dl & urine flow is 2 ml/min:
**Core Concept**
The clearance of a substance is a measure of the volume of plasma from which the substance is completely removed per unit time. It is an important concept in pharmacokinetics and renal physiology.
**Why the Correct Answer is Right**
The clearance of a substance can be calculated using the formula: Clearance (Cl) = (Urine concentration x Urine flow) / Plasma concentration. Given the values, Cl = (100 mg/dl x 2 ml/min) / 10 mg/dl = 20 ml/min.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not take into account the urine flow rate, which is a critical component of the clearance calculation.
**Option B:** This option is incorrect because it inverts the formula, resulting in an incorrect calculation.
**Option C:** This option is incorrect because it multiplies the urine concentration by the plasma concentration, which is mathematically incorrect.
**Clinical Pearl / High-Yield Fact**
When calculating clearance, remember the formula: Clearance = (Urine concentration x Urine flow) / Plasma concentration. This formula can be used to estimate the glomerular filtration rate (GFR) in patients with kidney disease.
**Correct Answer:** C.