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Article Review/Hyperlink
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Zaltzman JS, Whiteside C, Cattran C, Lopez FM, Logan AG
Accurate measurement of impaired glomerular filtration using
single-dose oral cimetidine
Am J Kidney Dis
(Apr) 27:504-511 1996

The creatinine clearance over some timed period remains the most
clinically practical measure of glomerular filtration. This in spite
of its known inaccuracies, principally due to the tubular secretion of
creatinine, yielding a clinically important overestimation of
glomerular filtration compared with iothalamate. With decreasing
renal function the proportion of creatinine secreted at the tubule
increases relative to that which is filtered at the glomerulus,
causing a further loss of accuracy in the creatinine clearance.
Previous studies have used cimetidine to inhibit the secretion of
creatinine during the timed creatinine clearance (TCCim) showing an
improved accuracy in patients with relatively preserved renal
function. Zaltzman et al. describe the use of cimetidine to improve
the measurement of glomerular function in patients with moderate to
severe renal insufficiency.
One hour following oral cimetidine 800mg a three hour timed urine
collection was obtained along with a midpoint serum creatinine. The
resulting creatinine clearance was calculated and compared to the
results of a simultaneously measured iothalamate clearance (Cioth) and
a timed clearance without cimetidine (TC) obtained on another
occasion. As expected the glomerular filtration based on TC
significantly overestimated that measured by Cioth with a TC/Cioth of
1.53. In contrast the TCC showed considerable accuracy with a
TCC/Cioth of 1.12.
Comment: The addition of cimetidine to the timed creatinine
clearance appears to add considerable accuracy to the resulting
estimate of glomerular filtration. This study demonstrates this point
in patients with moderate/severe renal dysfunction. The addition of
oral cimetidine adds little to the complexity or cost of the test, and
of course is far simpler and less expensive than measurements of
iothalamate or inulin clearances. It would be important to keep in
mind that the use of cimetidine to inhibit the tubular secretion of
creatinine can lead to a subsequent elevation in the serum creatinine.
This would likely be transient with the single dose protocol described
and would of course not reflect a true decrease in glomerular
function. Greg Cowell, M.D., University of Illinois at Chicago
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