Volume 188 - Issue 7
Chronic kidney disease and automatic reporting of estimated glomerular filtration rate: revised recommendations
Authors: Andrew J McLachlan, on behalf of the Editorial Advisory Board, Australian medicines handbook
Med J Aust 2008; 188 (7): 427-430. || doi: 10.5694/j.1326-5377.2008.tb01699.x
Published online: 7 April 2008
Published online: 7 April 2008
To the Editor: The revised recommendations for the use of the estimated glomerular filration rate (eGFR) in the clinical setting use the Modification of Diet in Renal Disease (MDRD) formula to adjust drug dosing in people with renal impairment (Recommendation 6).1 Although the utility of the MDRD-based eGFR as a screening tool to identify people with chronic kidney disease represents an important clinical opportunity, we, and others,2,3 remain concerned about this recommendation.
Certainly, adjusting the dose of renally excreted medicines based on a patient’s serum creatinine concentration alone is not appropriate. Accordingly, many drug monographs provide explicit dosing recommendations based on the estimated creatinine clearance (calculated using the Cockcroft–Gault formula) as a rational basis for dose adjustment using sound pharmacological principles. This assumes a significant correlation between the estimated creatinine clearance and the actual clearance of a drug (or metabolite). But such a correlation has not been established for the MDRD formula.
Indeed, an empirical study comparing the use of the Cockcroft–Gault formula to the MDRD formula in 1067 elderly patients found that the MDRD formula significantly overestimated renal function and would, if used, lead to significantly higher doses of two drugs in question (enoxaparin and gentamicin) being administered.2 This highlights the need for further research to rigorously characterise the relationship between MDRD estimates of renal function and drug clearance before this formula can be recommended to guide dose adjustment in the clinical setting.
Recommendation 6, that the MDRD-based eGFR should be used for dosing after considering body size,1 requires further clinical information about the patient — the same information needed to use the Cockcroft–Gault formula. Even limiting Recommendation 6 to drugs that are not “critical-dose drugs”1 is confusing. Many drugs would be considered critical-dose drugs when used in frail older people with some degree of renal impairment.
We reaffirm the statement, from the 2008 Australian medicines handbook, that “there is no evidence that [automatically reported eGFR] is suitable for adjusting drug doses in people with renal impairment”.4
References
- Mathew TH, Johnson DW, Jones GRD, on behalf of the Australasian Creatinine Consensus Working Group. Chronic kidney disease and automatic reporting of estimated glomerular filtration rate: revised recommendations. Med J Aust 2007; 187: 459-463.
- Roberts GW. Dosing of key renally cleared drugs in the elderly — time to be wary of the eGFR. J Pharm Prac Res 2006; 36: 204-209. 0_i1091835
- Faull R. Prescribing in renal disease. Aust Prescr 2007; 30: 17-20. 0_i1091837
- Prescribing in renal impairment. In: Australian medicines handbook. Adelaide: AMH, 2008: xiv-xv. 0_i1091839