Creatinine clearance following cimetidine for estimation of glomerular filtration rate.

Simultaneous inulin (C[in]) and creatinine clearance (C[Cr]) studies were performed on 53 pediatric renal patients using a cimetidine protocol. Since cimetidine blocks the tubular secretion of creatinine, it was hypothesized that C(Cr) measured following cimetidine would closely approximate the C(in). C(in) was compared with C(Cr) with the latter calculated from: (1) a 24-h urine collection, (2) plasma creatinine, height, and a proportionality constant, (3) the same plasma and urine specimens used for calculating C(in), and (4) from the plasma and urine specimens of the four 30-min clearance periods treated as a single 2-h clearance. The C(in) was very closely approximated by the C(Cr) calculated from the same specimens used for the C(in) and by the 2-h clearance. The cimetidine protocol, with C(Cr) derived from a 2-h urine collection obtained under supervision in the office or clinic, provides a convenient and inexpensive procedure for estimation of glomerular filtration rate in a clinical setting.