ELIMINATION OF THE NONIONIC X-RAY CONTRAST-MEDIA IODIXANOL AND IOHEXOL IN PATIENTS WITH SEVERELY IMPAIRED RENAL-FUNCTION

Iodixanol (Visipaque(R)) and iohexol (Omnipaque(R)) are dimeric and mo nomeric, respectively, non-ionic X-ray contrast media (CM), with well- characterized pharmacokinetics in healthy volunteers. This study was u ndertaken to study the pharmacokinetics of the contrast media in patie nts with severely impaired renal function. A total of 16 patients refe rred for preoperative abdominal angiography were randomized to form tw o groups of eight patients, receiving either iodixanol 320 mgI ml(-1) or iohexol 350 mgI ml(-1). Urine and faeces were sampled before the ex amination and collected quantitatively for five days afterwards, and b lood samples were drawn frequently. The concentrations of iodine and c ontrast medium in urine and in serum, and the amount of iodine in faec es were determined. Mean baseline creatinine clearance was 13.6 and 9. 9 ml min(-1) 1.73 m(-2) in the iodixanol and iohexol groups, respectiv ely. Patients in the iodixanol group received on average 0.34 gI per k g bodyweight (bw) and those in the iohexol group 0.39 gI per kg bw. Th e semilogarithmic plots of serum concentration of CM vs. time indicate d elimination according to a two-compartment model. The mean eliminati on half-life was 23.0 h for iodixanol and 27.2 h for iohexol, and the mean apparent volume of distribution was similar for the two CM, rangi ng from 0.20 to 0.30 1 per kg bw. Mean plasma clearance of iodixanol w as 10.4 ml min(-1) 1.73 m(-2) and 6.9 ml min(-1) 1.73 m(-2) for iohexo l, whereas the mean renal clearances were 8.7 and 6.1 ml min(-1) 1.73 m(-2), respectively. Mean faecal recovery was 8.2% for iodixanol and 6 .1% for iohexol, and the respective figures for that in urine were 76. 1 and 74.8%. Renal clearance of radiolabelled iothalamate, a marker of glomerular filtration rate (GFR), measured simultaneously, indicated that both CM were eliminated by the kidneys by glomerular filtration o nly. Thus, both media are suitable as GFR markers.