Quantifying Renal Function

Glomerular filtration rate, the volume of plasma filtered across the glomerulus per unit time

We use eGFR (estimated) since GFR cannot be directly measured

Used for identifying what stage of kidney disease patients have, not generally used for drug dosing

Male
Meat ingestion
Muscle content
younger age

Metformin

SGLT2 inhibitors (Empagliflozin, Dapagliflozin, Canagliflozin (flozins))

Allopurinol

Some oncology medications

Ideal body weight (IBW) for most patients, unless actual body weight (ABW) is lower than IBW, in which case you use ABW, or if the patient is 1.3 times heavier than their IBW, in which case you use AdjBW.

Additionally, there are some drugs that are always dosed using the ABW in the cockcroft-gault equation

Dabigatran (Pradaxa®)

Rivaroxaban (Xarelto®)

Dofetilide (Tikosyn®)

Zolendronic acid (Reclast®)

If the patient is undergoing acute renal function changes, such as acute renal failure. SCr lags behind the actual CrCl and is unreliable in these situations, assume patients with renal failure who are not producing urine have a CrCl of 10-15 mL/min

If a patient's renal function is trending up and SCr levels are decreasing, then the actual CrCl is likely higher than what is estimated with the CrCl equation. Conversely, if renal clearance has been worsening, and SCr levels are rising, the actual CrCl is likely lower than what is estimated.

After undergoing 6 months of hormone therapy. Prior to 6 months of therapy, calculate CrCl based on sex assigned at birth

Drugs that interfere with assay:

Flucytosine

Cefoxitin

N-acetylcysteine

Drugs that decrease SCr secretion into urine:

Cimetidine

Ranitidine

Trimethoprim

Triamterene