Nonionic dimers

Table 5. Properties of Nonionic Dimeric Contrast Media ...

In the 1990s, to achieve iso-osmolality with plasma, various teams synthesized nonionic dimers, which resulted in the marketing of iotrolan and iodixanol. However, these compounds suffer from high levels of viscosity (at 20 °C and 320 mgl mL h iodixanol = 25.4 mPa.s vs 15.7 mPa.s for the ionic dimer sodium/ meglumine ioxaglate). 

Mixanol. lodixanol is a luw-osmolar nonionic dimeric contrast agent. It is designed for intravascular injection and i.s used for excretory urography, angiography, and CT. 

D. Nonionic dimers or bis compounds l.Bis-triiodo-l,3-benzenedicarboxainides (10,10 ) lodecol (a) lodixanol (b) lotasul (c) lotrolan (or iotrol) (d) lofratol (e) E. Miscellaneous ... 

Iodinated nonionic dimers iodixanol, iode-col, iofratol, and iotrol (or iotrolan) have respectively lower osmolalities (200, 320, 140, and 320 mOsm/kg HgO) and higher viscosities (8.7, 7.2, 8.5, and 8.1 mPa-s at 37°C) than those of iodinated nonionic monomers. Felder and de Haen (429) found unexpectedly that solution mixtures of iodinated nonionic monomers and dimers, such as iomeprol and iofratol, have a lower toxicity and a lower viscosity than those of either of the components and can supply a favorable iodine delivery rate through less invasive catheters during the injection, but have an intermediate osmolality compared to that of the pure solutions of the monomer and dimer components. 

Ionic contrast monomers at a solution concentration of 300 mg I/mL have an osmolality in the range of 1.5-1.7 Osm/kg HgO. At the same solution concentration, nonionic monomers, monoacidic ionic dimer (ioxaglate), and nonionic dimers have osmolalities of 0.6-0.7, 0.56, and about 0.3 Osm/kg, respectively. If... 

Muschick et al. (596) compared the hemodynamic effects of 11 iodinated contrast media, including ionic (diatrizoate, ioxaglate), nonionic monomers (iohexol, iopromide, iopamidol, iopentol, ioversal, iomeprol), and nonionic dimers (iotrolan. iodixanol) in rats. The animals were injected with contrast me-... 

Langner S, Stumpe S, Kirsch M et al (2008) No increased risk for contrast-induced nephropathy after multiple CT perfusion studies of the brain with a nonionic, dimeric, iso-osmolal contrast medium. Am J Neuroradiol 29 1525-1529. 

In Equation 3.26, T is the equilibrium surface excess, C the bulk concentration, t the time, and D the surfactant monomer diffusion coefficient. Eastoe et al. have measured the time dependence of the DST and the relaxation time %2 for solutions of many surfactants nonionic, dimeric, and zwitterionic. In all instances the fitting of the data to Equation 3.26 with the experimentally determined value of %2 was poor. The authors concluded that the micelle dissociation may have an effect on the measured DST only if the concentration of monomeric surfactant in the subsurface diffusion layer is limiting or when the micelle lifetimes are extremely long. No surfactant for which this last condition is fulfilled was evidenced by the authors. They also concluded that the rapid dissociation of monomers from micelles present in the subsurface was not likely to limit the surfactant adsorption and thus the DST. 

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