Influence of equation used to estimate the renal function in dosage potentially nephrotoxic drug

Objective To evaluate the similarity (or not) of the dose recommendations according to the Cockcroft–Gault and MDRD4 (modified diet in renal disease) equations. Method A cross-sectional comparative observational test of patients suffering chronic renal illness that involved treatment using nephrotoxic drugs, admitted consecutively to the internal medicine department over a period of 6 months. The glomerular filtrate rate was calculated upon admission and at discharge using the Cockcroft–Gault and MDRD4 formulas. Grading of the disease for patients and dose adjustment recommendations of potentially nephrotoxic drugs was compared. The degree of correlation between the results obtained with both equations was assessed by means of the Pearson9s coefficient (r), considering p<0.05 as significant. Results Among the 249 patients included in the study, the staging of the disease was modified in 166 and the recommended dosage would have differed in 56.0% of these. Of the 222 prescriptions of potentially nephrotoxic drugs, 145 dosage adjustment recommendations would have differed. Glomerular filtrate rates were always less when the Cockcroft–Gault equation was used, although they were closely correlated both upon admission and discharge (Pearson9s r=0.83 and 0.81, respectively, p<0.001). Conclusions Although the Cockcroft–Gault and MDRD4 equations were statistically well correlated, differences in drug dose recommendations were noticeable.