Immediate adverse drug reactions in computed tomography with slow injection rate: Comparing iothalamate meglumine with iopromide

Non-ionic iodinated contrast media (NICM) are believed to cause less immediate adverse drug reactions (ADRs) than ionic iodinated contrast media (ICM). We undertook an observational study to compare the immediate ADRs caused by ICM and NICM during computed tomography (CT) examinations with a slow injection rate not greater than 2.0 mL/sec. This study was designed to compare the immediate ADRs by using Iothalamate meglumine (Conray®60%) and Topromide (Ultravist®370) for patients undergoing CT examinations in a period of 8 months. The injection rate was equal or less than 2.0 mL/sec. Immediate ADRs were classified by severity grading system. The statistical methods used were Fisher's exact test and odds ratio with 95% confidence intervals. Totally 8776 subjects were enrolled in our study, including 2766 subjects using Iothalamate and 6010 subjects using Iopromide. The overall incidence of immediate ADRs had statistical but small difference (p=0.04) between Iothalamate (1.84%) and Iopromide (1.26%). In each group classified by severity grading system, the incidence of immediate ADRs between subjects using Iothalamate and Iopromide did not show statistical difference. Under the setting of slow injection rate (≦ 2mL/sec), Iothalamate was associated with a higher total incidence of immediate ADRs than Iopromide, but the difference was small. When patients were classified into groups of different ADR severity, no significant difference was found between these two contrast media. Therefore, at an injection rate not greater than 2.0 mL/sec, using Iopromide may not cause less immediate ADRs than using Iothalamate.