131I-Iodohippurate (OIH)

Description

¹³¹I-Iodohippurate (also known as ¹³¹I-orthoiodohippurate or ¹³¹I-OIH) is a radiopharmaceutical agent designed for kidney imaging and function evaluation. It is specifically utilized for assessing tubular secretion, a critical parameter in renal function studies. This tracer has been a valuable tool in nuclear medicine for decades, helping clinicians gain insights into renal blood flow, tubular activity, and overall kidney performance.

Clinical Applications

¹³¹I-Iodohippurate serves as an effective diagnostic agent for identifying and evaluating various renal conditions, including:

• Kidney Failure: Assists in determining the extent and nature of renal dysfunction.
• Urine Outflow Disorders: Aids in diagnosing conditions such as obstructive uropathy.
• Kidney Blood Flow Evaluation: Provides information on renal perfusion and vascular integrity.
• Tubular Function Assessment: Offers insight into renal tubular activity and secretion efficiency.
• Post-Transplant Evaluation: Detects dysfunction or rejection in kidney transplant cases.

This radiopharmaceutical is administered in doses ranging from 0.1 to 2 mCi, depending on the diagnostic requirements and patient condition.

Availability

Currently, ¹³¹I-OIH is commercially available through IDB/AAA under the trade name Hipuran™. However, several formulations previously available in the market have been discontinued, including:

• HIPPI-131 (CISbio/IBA Molecular; EU Marketing Authorization in 2000)
• Hippuran I-131 (Mallinckrodt; US MA 1968; EU MA 2003, discontinued)
• Hippurate (POLATOM)
• Hipputope (Bracco; MA 1970)
• Iodohippurate (Pharmalucence)

These discontinuations reflect a broader trend of declining production due to the emergence of alternative imaging agents.

Competition

The use of ¹³¹I-Iodohippurate has been gradually declining in nuclear medicine, primarily due to the availability of newer and more versatile tracers. Competing agents such as ^99mTc-MAG3, DTPA, DMSA, and EC offer broader applications, improved accessibility, and lower costs. Despite this, ¹³¹I-OIH is regarded as slightly superior to ^99mTc-DTPA in imaging patients with renal failure due to its better renal function visualization capabilities.

Comments

Both ¹²³I-Iodohippurate and ¹³¹I-Iodohippurate are radiotracers that face increasing competition from alternative low-cost generic agents. These products are gradually losing prominence in nuclear medicine portfolios as manufacturers focus on higher-priority agents with greater demand and broader applications. The declining utilization of ¹³¹I-OIH reflects the evolution of nuclear medicine, with more advanced tracers taking precedence in clinical practice.