ALLIE PUNKE PHARMCOKINETICS

KIDNEY FUNCTION FOR DRUG DOSING

KIDNEY FUNCTION Patient A SCr=1, Patient B SCr=1.5. Which has better renal function? Cannot just look at SCr. Must use an equation to estimate CrCl or eGFR.

KIDNEY FUNCTION Cockcroft-Gault accounts for what factors: MDRD accounts for what factors:

KIDNEY FUNCTION CKD-EPI accounts for what factors:

KIDNEY FUNCTION Don’t need to memorize these equations, but you should know the factors that each equation accounts for.

KIDNEY FUNCTION T/F: When developing the Cockcroft Gault equation, a large population consisting of equal men and women were studied. T/F: Creatinine is only filtered. T/F: When developing the MDRD equation, a very small population with a majority of men were used in comparison to the Cockcroft Gault equation T/F: MDRD has a tendency to overestimate GFR at higher levels. T/F: When developing the MDRD equation, a wider population was used than in developing the CKD-EPI equation

KIDNEY FUNCTION T/F: Overall, Estimation of GFR using MDRD was better than using Cockroft-Gault.

KIDNEY FUNCTION Why do we need to use a “standardized” creatinine? A. The Jaffe method underestimated creatinine, which caused an overestimation of kidney function B. This is done to account for creatinine’s filtration and secretion C. The Jaffe method overestimated creatinine, which caused an underestimation of kidney function D. Because other blood constituents emit in the same spectrum as creatinine during the Jaffe method, which causes an overestimation of kidney function

KIDNEY FUNCTION

Problems with using creatinine as a marker of kidney function: Muscle mass/diet Also secreted  can overestimate Advantages of using cystatin C as a marker of kidney function: Only filtered (not secreted, unlike creatinine) Not dependent on age, sex, or muscle mass

KIDNEY FUNCTION When would additional tests (measuring CrCl or using another marker like cystatin C) likely not be needed? A. Patient with stable kidney function being started on atorvastatin following a MI B. Patient with variable kidney function being started on chemotherapy with kidney-dependent dosing C. Patient whose eGFR and CrCl give different results D. Patient who recently had his leg amputated

KIDNEY FUNCTION If you were to use an eGFR for drug dosing, what must you do to it?

KIDNEY FUNCTION Calculate the measured creatinine clearance for a patient with the following variables: Ucr=104, Volume= 1450, SCr=3 Know how to give patient directions undergoing this process.

QUESTIONS? GOOD LUCK!