Diatrizoate osmolality

The first modern hydrophilic nonspecific iodinated CA was diatrizoic acid, which, formulated as a sodium and/or meglumine salt, is still used. This agent was first synthesized in 1953 [1]. Osmolality for this compound, at concentrations compatible with imaging (ie. 300-370 mgl mL" ), is about 5-7 times that of plasma (1500-2100 mOsm kg H2O). Other HOCA such as iothalamate, metrizoate and ioxithalamate, were synthesized and marketed over the next few years. In an attempt to reduce the osmolality of the injected solution and thus reduce pain and haemodynamic disturbances, metrizamide, a compound resulting from the condensation of metrizoic acid and glucosamine, was synthesized. It was the first nonionic CA. 

CM can be classified according to osmolality, which reflects the total particle concentration of the solution (the number of molecules dissolved in a specific volume) (1,2), CM with osmolality greater than that of blood may be more difficult for the kidney to excrete. Over the past 40 years, the osmolalities of available CM have been gradually decreased to physiologic levels. In the 1950s, only high-osmolar CM (e.g., diatrizoate)... 

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