Comparative safety of intrathecal lopamidol vs. Metrizamide for myelography and cisternography

A new, nonionic iodinated contrast medium, iopamidol, was compared with metrizamide in a randomized, double-blind clinical trial for lumbosacral (n = 60) and cervical (it = 20) myelography and cisternography (n = 10). A dose of 12 to 14 mi of 200 mg I/ml was used for all the studies. The cervical myelograms were done via Cl-2 puncture. Film quality and diagnostic accuracy were equal in both groups. Although iopamidol caused less severe nausea and headaches, the most striking (and highly significant) difference involved the incidence of neurobehavioral (encephalo- pathic) adverse reactions, which occurred in 22% of metrizamide studies and none of the iopamidol studies. EEG slowing was also far more common with metrizamide (33%). Both agents entered the superficial brain substance after a few hours’ delay. Iopamidol was predominantly cleared from the subarachnoid space and bloodstream within 24 hours as determined by computed tomographic (CT) and fluorescent excitation analysis (FEA). The data strongly suggest that iopamidol is the agent of choice for intrathecal use.