Plasma clearance of a new contrast agent, iohexol: a method for the assessment of glomerular filtration rate.

We developed a rapid and precise method for the chemical determination of a new contrast agent, iohexol (N,N'-bis(2,3-dihydroxypropyl)-5-N-(2,3-dihydroxypropyl)-acetamido-2,4, 6-triiodoisophtalamide). Its sensitivity allows the monitoring of plasma concentrations for at least 6 hours after the injection of a single small dose. The elimination rate of iohexol was constant after approximately 90 minutes; plasma clearance in healthy volunteers averaged 127 ml/min. The injected dose was quantitatively recovered in urine. Determination of plasma clearance on two different occasions demonstrated a total variation of 11% (coefficient of variation); the methodologic imprecision was minor compared with the biologic variation. In 42 patients with normal to moderately impaired renal function, a comparison of iohexol and 51Cr-ethylenediaminetetraacetic acid clearances demonstrated an excellent correlation (correlation coefficient 0.98). The simplicity and rapidity of the new method makes it an attractive alternative to current methods for the assessment of glomerular filtration rate.