Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations.
BACKGROUND
Kidney disease alters the pharmacokinetic disposition of many medications, requiring dosage adjustment to maintain therapeutic serum concentrations. The Cockcroft-Gault (CG) equation is used for pharmacokinetic studies and drug dosage adjustments, but the Modification of Diet in Renal Disease (MDRD) Study equation is more accurate and more often reported by clinical laboratories than the CG equation.


METHODS
Diagnostic test study.


METHODS
Pooled data set for 5,504 participants from 6 research studies and 4 clinical populations with measured glomerular filtration rate (GFR).


METHODS
Estimated kidney function using the MDRD Study and CG equations incorporating actual (CG) or ideal body weight (CG(IBW)) and standardized serum creatinine concentrations.


METHODS
Measured GFR assessed by using iodine-125-iothalamate urinary clearance.


RESULTS
Concordance of assigned kidney function categories designated by the Food and Drug Administration (FDA) Guidance for Industry for pharmacokinetic studies and recommended dosages of 15 medications cleared by the kidneys.


RESULTS
Concordance of kidney function estimates with measured GFR for FDA-assigned kidney function categories was 78% for the MDRD Study equation compared with 73% for the CG equation (P < 0.001) and 66% for the CG(IBW) equation (P < 0.001). Concordance between the MDRD Study equation and CG and CG(IBW) equations was 78% and 75%, respectively (P < 0.001). Concordance of kidney function estimates with measured GFR for recommended drug dosages was 88% for MDRD Study equation compared with 85% for the CG equation (P < 0.001) and 82% for the CG(IBW) equation (P < 0.001), with lower concordance when dosing recommendations for drugs included narrow GFR ranges. Concordance rates between the CG and CG(IBW) equations and MDRD Study equation were 89% and 88%, respectively (P < 0.05).


CONCLUSIONS
Results based on simulation rather than pharmacokinetic studies. Outcome was drug dosage recommendations, rather than observed drug efficacy and safety.


CONCLUSIONS
The MDRD Study equation can also be used for pharmacokinetic studies and drug dosage adjustments. As more accurate GFR-estimating equations are developed, they should be used for these purposes.
Stevens
Lesley A
LA
Division of Nephrology, Tufts Medical Center, Boston, MA 02111, USA. lstevens1@tuftsmedicalcenter.org
Nolin
Thomas D
TD
Richardson
Michelle M
MM
Feldman
Harold I
HI
Lewis
Julia B
JB
Rodby
Roger
R
Townsend
Raymond
R
Okparavero
Aghogho
A
Zhang
Yaping Lucy
YL
Schmid
Christopher H
CH
Levey
Andrew S
AS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood; D054796:Drug Dosage Calculations; D004345:Drug Industry / Q000592:standards; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006287:Health Planning Guidelines; D006801:Humans; D007668:Kidney / Q000502:physiology*; D007674:Kidney Diseases / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D014481:United States; D014486:United States Food and Drug Administration
D003404:Creatinine