HDCN Article Review/Hyperlink

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