Indium-111 diethylenetriaminepentaacetic acid (In-111 DTPA)

Indium-111 diethylenetriaminepentaacetic acid (In-111 DTPA), also referred to as Indium In 111 Pentetate, is a specialized radiopharmaceutical diagnostic agent used primarily in nuclear medicine for imaging cerebrospinal fluid (CSF) dynamics. It consists of the gamma-emitting radionuclide Indium-111 securely bound by the chelating agent pentetic acid (DTPA), ensuring that the radioactive metal remains in a stable, non-dissociated form within the body (FDA Label, 2023). When injected into the spinal canal via lumbar puncture, it acts as a marker to visualize CSF circulation, absorption, and potential leakage sites, which is critical for diagnosing conditions such as hydrocephalus or CSF rhinorrhea (StatPearls, 2023). Due to its pharmacokinetic properties, it is also utilized to calculate the glomerular filtration rate (GFR), as the kidneys clear the complex almost entirely through glomerular filtration (PubChem). In-111 DTPA is categorized as a diagnostic agent rather than a therapeutic target because it does not bind to specific biological receptors to exert a pharmacological effect; instead, it tracks the physical movement of fluid. Its clinical utility is defined by its ability to provide high-contrast imaging of fluid flow with a half-life of approximately 2.8 days, which is suitable for multi-day cisternography studies (NCBI, 2023).

Other names

Indium In 111 PentetatePentetate indium disodium In-111Indium-111 DTPA111In-pentetateDTPA-In-111

Indium-111 DTPA is a diagnostic radiopharmaceutical that functions as a passive tracer for physiological fluid kinetics. After intrathecal administration, the chelated complex distributes within the subarachnoid space and follows the natural bulk flow of cerebrospinal fluid (CSF) toward the arachnoid villi, enabling the scintigraphic visualization of CSF pathways and the identification of obstructions or leaks (StatPearls, 2023). In the kidneys, the molecule is cleared exclusively by glomerular filtration without significant tubular secretion or reabsorption, serving as an indicator of glomerular filtration rate (FDA Label, 2023).