Table 1.
Iodinated contrast media commonly used in clinical practice.
| Name | Type | Iodine content | Osmolality | Osmolality type |
|---|---|---|---|---|
| (mg/mL) | (mOsm/kg) | |||
| Ionic | ||||
| Diatrizoate (Hypaque 76) | Monomer | 370 | 2,016 | HOCM |
| Metrizoate (Isopaque 370) | Monomer | 370 | 2,100 | HOCM |
| Iothalamate (Conray 400) | Monomer | 400 | 2,300 | HOCM |
| Ioxaglate (Hexabrix) | Dimer | 320 | 580 | LOCM |
| Nonionic | ||||
| Iopamidol (Isovue 370) | Monomer | 370 | 796 | LOCM |
| Iohexol (Omnipaque 350) | Monomer | 350 | 884 | LOCM |
| Iopromide (Ultravist 370) | Monomer | 370 | 774 | LOCM |
| Ioversol (Optiray 350) | Monomer | 350 | 792 | LOCM |
| Iomeprol (Iomeron 400) | Monomer | 400 | 720 | LOCM |
| Iobitridol (Xenetix 350) | Monomer | 350 | 915 | LOCM |
| Iodixanol (Visipaque 320) | Dimer | 320 | 290 | IOCM |
| Iotrolan (Isovist 300) | Dimer | 300 | 320 | IOCM |
Ionic and nonionic contrast media may be monomeric or dimeric; 3 iodine atoms are present on each benzene ring of the contrast medium: if a contrast molecule contains only 1 benzene ring, it is called a monomer, if it contains 2 benzene rings, it is called a dimer. In solution, ionic contrast media break up into their anion and cation components, thereby increasing osmolality, while nonionic contrast media do not break up in solution. Nonionic dimers are the ideal contrast media as they deliver the most iodine with the least effect on osmolality.
The osmolality of contrast media is compared with the osmolality of plasma. HOCM (high-osmolar contrast media) have the highest osmolality, that is, 5–8 times the osmolality of plasma. LOCM (low-osmolar contrast media) have an osmolality still higher than plasma, which is, 2-3 times the osmolality of plasma. IOCM (iso-osmolar contrast media) have the same osmolality as plasma.