Estimates of glomerular filtration rate (GFR) are used to
estimate renal function, in diagnosing renal disease and
are also used to estimate renal drug clearance. Some active
drug moieties are wholly or partly cleared from the body
by the kidneys and this is the physiological rationale for
using eGFR to estimate drug clearance. Similar to serum
drug concentration, serum creatinine is dependent on both
creatinine production (equivalent to drug dose) and creatinine
clearance (equivalent to renal drug clearance).
Serum creatinine is the most commonly used analyte in the
evaluation of renal function, and equations using serum
creatinine concentration are the basis of most estimates of
GFR (as discussed in detail elsewhere in this issue).1
Estimated
GFR (eGFR) has the units mL/min/1.73m2
,
2
whereas
creatinine clearance and drug clearance are both measured in
mL/min. To avoid confusion, units should be carefully noted
and their implications considered. This is discussed in more
detail below.