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Estimate renal function before selecting doses for renally eliminated drugs

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Most decisions about drug dosing for renally excreted drugs can be made based on the estimated GFR. Clinically, creatinine clearance is used to estimate GFR. Serum creatinine alone is not a good indicator of renal function in the elderly population because muscle mass, and therefore creatinine production, declines with age. A normal serum creatinine can result when both creatinine formation and elimination are reduced. Several algorithms have been proposed to estimate creatinine clearance. One frequently used method was developed by Cockcroft and Gault1, where creatinine clearance (CLcr) is calculated based on the patient's age, weight, and serum creatinine concentration: For females, the result is multiplied by 0.85. This formula is less accurate for estimates in the very high or low range and when renal function is changing rapidly. For frail elderly patients with chronic muscle atrophy, an alternative formula has been proposed2 that takes into account serum albumin levels as well. For men: For women: This approach provides more accurate and less biased estimates of CLcr than the Cockcroft and Gault method in elderly patients with renal insufficiency or serum albumin levels less than 2.8 g/dL.

Estimate renal function before selecting doses for renally eliminated drugs.

References:

1. Nephron 1976;16:31-41.
2. Sanaka M, et al. Nephron 1996;73:137-144.