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A rabbit model was used to assess the effects of intracarotid injections of ionic monomer (meglumine iothalamate), non-ionic monomer (iohexol, iopromide), and non-ionic dimer (iotrol) contrast materials on the blood-brain barrier. The degree of blood-brain barrier damage was assessed qualitatively using Evans' blue dye, and quantitatively by calculating the difference in pertechnetate uptake between injected and non-injected hemispheres. The results showed that the non-ionic dimer, iotrol, had the least effect on the blood-brain barrier, and that although iopromide and iohexol produced greater damage than iotrol, the ionic compound, meglumine iothalamate, caused the greatest disruption to the blood-brain barrier. The implications of these findings are discussed.

The incidence of post-myelographic side-effects has been significantly reduced since the advent of the new generation of water-soluble, non-ionic, contrast media (CM). One of these CM, iopamidol, has recently been released for clinical intrathecal use in Australia. Clinical evaluations have shown iopamidol to give excellent diagnostic results. However, many adverse side-effects have been cited in the literature. Reactions to iopamidol following myelography are thought to be due to the lack of a physiologic barrier between the extracellular fluid of the brain parenchyma and the CSF, thereby allowing CM to penetrate the brain parenchyma tissue, following subarachnoid injection. This study investigates the rate of clearance of intrathecal iopamidol from the brain in dogs by performing coronal CT scans at intervals over a 48 h, post-injection period. Analysis of similar regions of interest (ROI) for each time period indicate that iopamidol can be detected in canine brains for at least 48 h following intrathecal injection (P less than 0.05). Furthermore, the disappearance of iopamidol from the brain parenchyma is approximately logarithmic in form, with a half-life of approximately 22 h.