Comparative investigation of IV iohexol and iopamidol: Effect on renal function in low-risk outpatients undergoing CT

OBJECTIVE. The purpose of our study was to compare the effects of IV iohexol and iopamidol on renal function in outpatients undergoing CT. SUBJECTS AND METHODS. We performed a prospective, double-blind, randomized clinical trial of 389 adults with low risk for contrast-induced nephropathy, comparing IV iohexol with iopamidol (300 mg I/mL). Serum creatinine (SCr) concentration was measured at baseline and 2 and 3 days after contrast administration. A noninferiority analysis was planned to compare the mean maximum SCr change from baseline between subject groups. Contrast-induced nephropathy rates (three definitions) for both contrast agents were compared as a secondary end point. RESULTS. One hundred ninety and 199 subjects received iohexol and iopamidol, respectively. The mean change in SCr from baseline using the maximum day 2 or 3 measurement was 0.07 ± 0.12 mg/dL (95% CI, 0.05-0.09 mg/dL) for the iohexol group and 0.05 ± 0.12 mg/dL (95% CI, 0.03-0.07 mg/dL) for the iopamidol group. The difference between contrast agents with respect to the mean change in SCr from baseline was -0.02 ± 0.12 mg/dL (95% CI, -0.045 to 0.003 mg/dL; p = 0.08). Contrast-induced nephropathy rates were not statistically different using any definition. CONCLUSION. Although our results were unable to show absolute noninferiority of iohexol compared with iopamidol because of a very small difference in increase in mean SCr from baseline (using a noninferiority margin of 0.04 mg/dL), this difference is likely of minimal or no clinical importance in outpatients undergoing CT with low risk for contrast-induced nephropathy.