The first-generation contrast agents were all ionic monomers, consisting of a tri-iodinated benzene ring with 2 organic side chains and a carboxyl group. Diatrizoate or iothalamate are common iodinated anions, conjugated with a cation, sodium or meglumine. The ionization at the carboxyl-cation bond makes the agent water soluble.
Ionic monomers have the highest osmolality (high-osmolar contrast media (HOCM) possess an osmolality seven to eight times higher than plasma) of the different groups of contrast agents (CM ratio=1.5) and the lowest viscosity. The osmolality in solutions of ionic monomers ranges from 600 to 2100 mOsm/kg (human plasma = 290 mOsm/kg). These high osmolality is related to some of the adverse reactions. HOCM's have been widely replaced by newer contrast agents with improved tolerability and safety profiles.
Examples of HOCM's are Renografin®-60, Hypaque 76, Hypaque Meglumine, Hypaque Sodium and Conray®.

See also Ionic Contrast Agents.

Reno-30® is a radiopaque contrast agent indicated for retrograde or ascending pyelography. Retrograde pyelography does not include systemic administration of contrast media, so the risk of adverse reactions is extremely rare.

Reno-60® is radiopaque contrast agent with a wide range of indications. Reno-60 should be at body temperature when injected and may need to be warmed before use. Following intravascular injection, iodinated contrast materials are transported through the bloodstream to the kidneys and excreted by glomerular filtration.