Comparative effects of ionic and nonionic iodinated low-osmolar contrast media on platelet function with the PFA-100...

This study was designed to (1) compare the effects of ionic (ioxaglate) and nonionic (iodixanol and iohexol) iodinated low-osmolar contrast media (CM) on platelet function in human whole blood by using the new PFA-100trade mark, a "platelet function analyzer"; (2) determine the animal species closest to human with regard to platelet reactivity to CM; and (3) evaluate which element of the ioxaglate solution supports this activity.

For all studies, platelet adhesion and aggregation were measured using the PFA-100trade mark system with adenosine diphosphate-primed collagen membrane cartridges. Results are shown as the membrane closure time (MCT; the longer the MCT, the greater the antiaggregatory effect) and given as medians. Citrated whole-blood samples from six healthy volunteers were mixed for 1 minute with a 10% (vol/vol) solution of ioxaglate, iodixanol, or iohexol or their respective ionic and nonionic controls (isotonic saline and mannitol). The test solution/control solution ratio for the MCT was calculated for the blood of humans, guinea pigs, rabbits, dogs, and rats. Isotonic saline and iso-osmolar (280 mOsm/kg) and hyperosmolar (560 mOsm/kg) solutions of meglumine hydrochloride, meglumine ioxaglate (560 mOsm/kg), and sodium ioxaglate (600 mOsm/kg) were tested under similar conditions.

All three CM caused significant prolongation of MCT when compared with their respective controls (ioxaglate: 300 seconds, ie, "no closure" on the PFA-100trade mark system; iodixanol: 179 seconds; iohexol: 171 seconds; saline: 115 seconds; mannitol: 118 seconds). The antiplatelet effect of ioxaglate was higher than that of iodixanol and iohexol (P < 0.05). The animal species tested did not differ significantly from the human species with regard to an effect of their blood on MCT. Both ioxaglic acid salts caused a higher prolongation of MCT when compared with saline (sodium salt: 259 seconds; meglumine salt: 212 seconds; P < 0.05 vs. saline) but not versus the ioxaglate commercial solution. Conversely, both iso- and hyperosmolar solutions of meglumine hydrochloride (108 and 128 seconds, respectively) did not lengthen MCT versus saline, but their MCTs were shorter than that of the commercial solution of ioxaglate (P < 0.05).

The ionic CM ioxaglate displayed a greater antiaggregatory effect on human platelets than did both iso-osmolar (iodixanol) and hyperosmolar (iohexol) nonionic CM. This effect seems to be linked to the ioxaglic moiety, because neither osmolality nor sodium or meglumine appeared to play a significant role.