In the renal dose adjustment formula, KF is defined as which of the following?

In the renal dose adjustment formula, KF is defined as which of the following?

• A. CrCl ÷ 60
• B. CrCl ÷ 120
• C. CrCl ÷ 240
• D. CrCl ÷ 12

Answer: (B)

KF serves as a renal function correction factor by normalizing creatinine clearance to a standard reference value. The usual baseline for normal kidney function is CrCl about 120 mL/min, so KF is defined as CrCl divided by 120. This makes KF a fraction that represents how much renal function remains compared to normal. It’s used to scale dose or dosing interval for renally cleared drugs: a lower KF (reduced CrCl) means you lower the dose or lengthen the interval, while KF near 1 means standard dosing. For example, CrCl = 60 mL/min gives KF ≈ 0.5, leading to dose reduction or interval extension. The divisor 120 reflects the normal CrCl, not 60, 240, or 12, which is why CrCl ÷ 120 is the correct way to define KF.

KF serves as a renal function correction factor by normalizing creatinine clearance to a standard reference value. The usual baseline for normal kidney function is CrCl about 120 mL/min, so KF is defined as CrCl divided by 120. This makes KF a fraction that represents how much renal function remains compared to normal. It’s used to scale dose or dosing interval for renally cleared drugs: a lower KF (reduced CrCl) means you lower the dose or lengthen the interval, while KF near 1 means standard dosing. For example, CrCl = 60 mL/min gives KF ≈ 0.5, leading to dose reduction or interval extension. The divisor 120 reflects the normal CrCl, not 60, 240, or 12, which is why CrCl ÷ 120 is the correct way to define KF.