125I-Human Serum Albumin (HSA)
December 24, 2024
Description:
Iodinated Human Serum Albumin labeled with iodine-125 (125I-HSA) is a specialized radiopharmaceutical used for measuring plasma volume (PV) and total blood volume (TBV). Its unique properties make it indispensable for certain clinical and research applications.
Clinical Applications
125I-HSA is a powerful tool in biological analysis, particularly for determining plasma volume and total blood volume. Additionally, it is utilized in studies of albumin turnover to evaluate protein metabolism and circulation.
A significant advantage of 125I-HSA is that it requires only trace amounts of radioactive material since imaging is not involved in its use. Despite advances in alternative radiopharmaceuticals, 125I-HSA remains superior for specific applications. For example, a 2012 study highlighted that while technetium-99m-labeled human serum albumin (99mTc-HSA) offers similar precision in measuring PV, it tends to consistently overestimate PV, particularly in patients with liver disorders. Consequently, 99mTc-HSA is unsuitable as a replacement for 125I-HSA in such cases.
Availability
125I-HSA is produced by select manufacturers and is available under various brand names, including:
- Jeantope I-125: Manufactured by Iso-Tex Diagnostics (approved in 1976, distributed by IDB/AAA).
- IHSA-I125: Previously distributed by Mallinckrodt under the brand Isojex® (now discontinued).
- SERALB-125: Manufactured by IBA Molecular (now Curium).
These limited production sources highlight the specialized and regulated nature of this substance.
Alternatives and Competition
Several alternatives to 125I-HSA have been explored:
- 99mTc-HSA: While offering comparable precision, its consistent overestimation of plasma volume, particularly in patients with liver conditions, limits its reliability.
- 131I-HSA: Another iodinated human serum albumin variant, 131I has shown promising reliability with the added advantage of a shorter half-life. However, its use is not as widespread as 125I-HSA.
Challenges and Future Use
With stricter regulations governing patient radiation doses and waste disposal of substances with long half-lives, the use of 125I-HSA is expected to decline over time. Its future application will likely be restricted to cases where no viable alternative exists, particularly in clinical scenarios requiring unparalleled accuracy in plasma volume measurement.
For now, 125I-HSA remains an irreplaceable tool for specific diagnostic and research needs, especially in scenarios where precision is paramount.