Estimated GFR vs creatinine clearance for drug dosing.

Stevens et al suggest that the Modification of Diet in Renal Disease (MDRD) Study equation for estimated glomerular filtration rate (GFR) is an acceptable substitute for estimated or measured creatinine clearance (CCr) as an index for adjusting drug doses in patients with chronic kidney disease and acute kidney injury. However, others have raised concerns that injudicious use of estimated GFR as a substitute for CCr could result in significant dosing errors and toxicity, especially for drugs with narrow therapeutic indices. Further, their conclusion is not supported by results of 4 studies that showed that using the MDRD Study equation instead of CCr estimates led to recommendations for 30%60% higher doses of digoxin, amantadine, and various antimicrobials. Estimated GFR values have also been shown to overestimate CCr in patients with measured GFRs_60 mL/min/1.73 m (_1 mL/s/1.73 m), the population most likely to require dose modification.