Analysis of the factors influencing the osmolality of eight monomeric nonionic iodinated contrast medium molecules.

Rationale And Objectives: Because the measured osmolality of a contrast medium solution differs considerably from the theoretical one, the author analyzed the relative influence of various parameters on the experimental osmolality and derived an equation permitting the prospective calculation of the real osmolality of monomeric nonionics. The author discusses the consequences of the results.

Materials: Eight monomer nonionic iodinated molecules (ioversol, iohexol, P-569, iobitridol, P-530, iopamidol, and iopromide) were analyzed. A parameter combining the hydrophilic and the hydrophobic aspects of these molecules was calculated, the relative weight of each composing term was calculated with the multiple nonlinear regression technique.

Results: The regression equation was determined based on seven compounds. A high proportion of explained variance was achieved. The prediction for ioxilan (with the lowest osmolality of the eight molecules) yielded a good result, confirming that structural influences determine the osmolality of a molecule.

Conclusions: The study of the parameters influencing the osmolality of eight nonionic iodinated monomer contrast medium molecules led to the development of a regression equation. It is shown that both the hydrophilic and hydrophobic characteristics of a molecule are important in the determination of the osmolality. This equation can be useful prospectively.