Topical intranasal ioxaglate meglumine 39.3% and ioxaglate sodium 19.6% (Hexabrix) reduces the acute response to nasal challenge with allergen

To the Editor: Ioxaglate meglumine 39.3% and ioxaglate sodium 19.6% (Hexabrix; Guerbet, Lyons, France) is a currently available intravenous contrast medium.1 One known side effect of intravenous contrast media is anaphylactoid reactions mediated through mast cell activation.2 Paradoxically, it was discovered that such media, at a higher concentration than used in radiology, had an inhibitory effect on mast cells.3 Investigations have shown that the mechanism of this inhibitory effect is through contrast media affiliating with the Fc (constant) part of the IgE molecule and subsequently preventing aggregation of IgE receptors and subsequent mast cell triggering.3 Contrast media also inhibited the attachment of antigens to their specific antibodies in an RBC hemagglutination inhibition study.3 In one of the experiments in this study, it was shown that contrast media could even dislodge an antigen that was already attached to its antibody.3 The potential inhibitory effect of contrast media on IgE-mediated histamine release was investigated in an animal model whereby rats sensitized to ovalbumin and challenged with the sensitizing antigen experience histamine-induced anaphylactic shock.4 Contrast media (vs equiosmolar saline) were injected intravenously in high concentrations at the nadir of the decrease in blood pressure and immediately restored normal pressures.