Abstract
OBJECTIVE
To describe a practical solution for addressing body weight when using the Cockcroft-Gault equation to determine drug dosing.
DATA SOURCES
A literature search was conducted using PubMed MEDLINE (1980-April 2013) using creatinine clearance, Cockcroft and Gault, Cockcroft-Gault, body weight, and obesity as search terms. Reference citations from publications reviewed were included.
STUDY SELECTION AND DATA EXTRACTION
All English-language articles identified by the search were reviewed. Studies comparing the accuracy and bias of the Cockcroft-Gault equation using a variety of body weight designations in adult populations were included in the analysis.
DATA SYNTHESIS
Study results indicated that, for obese patients, ideal body weight (IBW) underestimates creatinine clearance (CrCl) and total body weight (TBW) overestimates CrCl. Some studies suggest that adjusted body weight with a factor of 0.4 is most accurate, while others suggest the use of lean body weight. These studies have failed to produce a definitive resolution to the controversy. Despite many well-designed studies, the Cockcroft-Gault body weight controversy remains unresolved and uncertainty continues to exist as to which form of weight should be used in the equation. A different perspective is warranted. Since renal dosing guidelines are generally based on ranges of CrCl, applying a CrCl range to describe a patient's renal function might be more practical than relying on a specific CrCl value. Ultimately, CrCl-based drug dosing involves the use of an imperfect mathematical approximation, which is then applied as precisely as possible to the benefit versus risk analysis for a specific patient.
CONCLUSIONS
We propose the use of a CrCl range for drug dosing purposes, with the lower boundary defined by using IBW in the Cockcroft-Gault equation and the upper boundary by using TBW.
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