]> 2026-07-31T09:41:38+00:00 WBR0618 0 en A Creatinine secretion does not increase with use of cimetidine. B Creatinine secretion does not increase with use of cimetidine. C Cimetidine inhibits tubular secretion of creatinine. As such, creatinine clearance will decrease but calculated GFR based on creatinine will become closer to the true GFR, which is calculated by measuring inulin clearance. D Inulin clearance is not affected. E Absolute difference between both eGFRs should decrease. eGFR(creatinine) will be less of an overestimation of the true GFR. It will approach the GFR calculated by inulin clearance. The use of creatinine clearance for the estimation of the glomerular filtration rate (eGFR) generally overestimates the true GFR due to the combined filtration and secretion of creatinine along the renal tubules. As such, inulin remains the gold standard for the estimation of the GFR because it is only filtered and not secreted. Cimetidine, an H2 receptor blocker, blocks tubular creatinine secretion. Because cimetidine blocks the tubular secretion of creatinine, the creatinine clearance is decreased. The use of cimetidine allows only the filtration of creatinine to occur by preventing its secretion. Thus, the estimation of GFR based on creatinine clearance is expected to become more accurate with the use of cimetidine and approximate inulin clearance or the true GFR. Inulin clearance is not affected by cimetidine.<br/> '''Educational Objective:''' Cimetidine blocks the tubular secretion of creatinine, thus decreasing creatinine clearance. As such, creatinine will only be filtered and approximation of eGFR based on creatinine values becomes more accurate and closer to the true GFR.<br/> '''References:''' Van Acker BA, Koomen GC, Koopman MG, et al. Creatinine clearance during cimetidine administration for measurement of glomerular filtration rate. Lancet. 1992;340(8831):1326-9. Physiology C Renal 2020-10-28T01:11:39Z 2459150.5497569 WBR0618