Iothalamate Sodium

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Cat Number

API0231564

CAS Number

1225-20-3

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Product Detail Description Scientific Support Customer Q&A

CAS Number

1225-20-3

EINECS

214-955-8

Storage

Store at room temperature

Synonyms

Sodium iothalamate; Angio-Conray; Mediocontrix; Iothalamic acid sodium salt; KDN276D83N; DTXSID1057668; Monosodium 5-acetamido-2,4,6-triiodo-N-methylisophthalamate

Molecular Formula

C11H8I3N2NaO4

Molecular Weight

635.89

Smiles

CC(=O)NC1=C(C(=C(C(=C1I)C(=O)[O-])I)C(=O)NC)I.[Na+]

General Description

Iothalamate sodium is an ionic, high-osmolar, tri-iodinated radiographic contrast agent used primarily for urography, angiography, and computed tomography enhancement. It is available as a sterile solution for intravascular, intracavitary, or intrathecal administration, though its use has largely been replaced by low-osmolar and iso-osmolar agents. The compound contains three iodine atoms per molecule, providing excellent radiopacity.

Mechanism of Action

Iothalamate sodium attenuates X-rays due to the high atomic number of iodine, creating contrast between blood vessels, organs, and surrounding tissues. After intravascular injection, it distributes rapidly in the extracellular fluid and is excreted unchanged by the kidneys via glomerular filtration without tubular reabsorption or secretion. This pharmacokinetic profile makes it ideal for renal imaging, as the rate of contrast appearance and concentration reflects renal function.

Application

It is indicated for various radiographic procedures including intravenous urography, peripheral arteriography, coronary arteriography, and contrast-enhanced computed tomography. It is also used to measure glomerular filtration rate clinically, as its renal clearance closely approximates inulin clearance. Due to the risk of contrast-induced nephropathy and hypersensitivity reactions, including anaphylaxis, its use requires careful patient selection, particularly in those with pre-existing renal impairment or contrast allergy.

In 102 patients, the authors concomitantly measured GFR by plasma clearance of iohexol and iothalamate. When iohexol was measured by HPLC, there was no significant difference versus iothalamate (relative bias ‑2%, P=0.2). However, when iohexol was measured by LC‑MS/MS, clearance was 11% lower than iothalamate (P<0.001). Accuracy within 30% exceeded 98% for both methods. The authors note that iothalamate undergoes tubular secretion, so the lower values obtained with LC‑MS/MS iohexol might be closer to true GFR. They conclude that plasma clearance of either marker is acceptable for clinical routine, but the analytical method for iohexol influences results, a factor that should be considered in research settings.

Fig. 1 Passing-Bablok regressions: comparison of GFR measured by iohexol (y-axis) and iothalamate (x-axis). (Delanaye P, et al., 2016)

References

Delanaye P, et al. Concordance Between Iothalamate and Iohexol Plasma Clearance. Am J Kidney Dis. 2016; 68(2):329-330.

Does Iothalamate Sodium require protection from light during long-term storage?

Yes, it is photosensitive. Prolonged UV exposure can cause discoloration and degradation. Store in light-resistant, tightly sealed containers.

What is the recommended storage temperature for Iothalamate Sodium?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can accelerate decomposition and free iodine formation.

Is Iothalamate Sodium stable in solution for radiographic contrast media?

Formulated solutions are stable when stored at room temperature and protected from light.

How is the free iodine content monitored during stability?

Free iodide is quantified using ion chromatography or a validated colorimetric method, ensuring it remains below pharmacopoeial limits for injectable contrast agents.