As a hospital pharmacist, you can help colleagues determine the best way to estimate kidney function and adjust medications. Dosing based on estimated glomerular filtration rate (eGFR) is in labeling for more medications (meropenem/vaborbactam, baricitinib, etc). But CrCl and eGFR are NOT interchangeable, despite some guidance suggesting they are.
Using eGFR when you should use CrCl may miss dose adjustments up to 50% of the time especially in the elderly or patients with moderate to severe kidney impairment. Continue to follow med label recommendations for renal dosing...
If labels don't specify, look at the units. Use CrCl for mL/min, and eGFR for mL/min/1.73 m2. Verify the eGFR equation in your documents. It's now advised to calculate eGFR without using race, since it doesn't predict individual response. And don't automatically rely on your electronic calculation. For example, it won't tell you if a patient is on hemodialysis or receiving continuous renal replacement therapy (CRRT).
Continue to use ACTUAL body weight for CrCl if it's less than the patient's ideal weight. But generally, use an ADJUSTED body weight if the patient's weight is 20% to 30% higher than ideal. Equation to calculate adjusted body weight, available at (https://www.mdcalc.com/ideal-body-weight-adjusted-body-weight). When calculating eGFR in patients who are over- or underweight, multiply by their body surface area (BSA), then divide by 1.73 m2. This limits OVERestimating in small patients or UNDERestimating in large patients, since eGFR is based on a "normal" BSA.
Use clinical judgment when renal function is changing. For example, think about waiting 24 hours to renally adjust antibiotics when starting them in a septic patient with acute kidney injury. Read our note "Wait to RENALLY adjust antibiotics in septic patients" for more information.
Follow trends closely. For instance, we know serum creatinine (SCr) 0.8 mg/dL is in the normal range. But it's a significant change in a bedridden patient with a baseline SCr of 0.3 mg/dL and medications may need to be adjusted. Get our notes, "eGFR and Creatinine clearance" AND "Don't use estimated GFR to renally dose all medications" for more details.
REFERENCES
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Dowling TC, Wang ES, Ferrucci L, Sorkin JD. Glomerular filtration rate equations overestimate creatinine clearance in older individuals enrolled in the Baltimore Longitudinal Study on Aging: impact on renal drug dosing. Pharmacotherapy. 2013 Sep;33(9):912-21. Available at: https://accpjournals.onlinelibrary.wiley.com/doi/10.1002/phar.1282
National Institute of Diabetes and Digestive and Kidney Diseases. CKD & Drug Dosing: Information for Providers | NIDDK. [online] Available at: https://www.niddk.nih.gov/research-funding/research-programs/kidney-clinical-research-epidemiology/laboratory/ckd-drug-dosing-providers
Stevens LA, Nolin TD, Richardson MM, Feldman HI, Lewis JB, Rodby R, Townsend R, Okparavero A, Zhang YL, Schmid CH, Levey AS; Chronic Kidney Disease Epidemiology Collaboration. Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations. Am J Kidney Dis. 2009 Jul;54(1):33-42. Available at: https://www.ajkd.org/article/S0272-6386(09)00601-5/fulltext
National Kidney Foundation. (2021). Changes to eGFR Calculation and What that Means for People Living with Kidney Disease. [online] Available at: https://www.kidney.org/newsletter/changes-to-egfr-calculation-and-what-means-people-living-kidney-disease