DMSA and its complexes with radioisotopes: review

Abnormal Biologic Distribution Related to Normal Saline Among 99mTc-Dimercaptosuccinic Acid Scans

The primary aim was to describe the incidence and causes of abnormal distribution of ^99mTc-dimercaptosuccinic acid (^99mTc-DMSA) among patients who underwent renal scans in Royal Hospital (Oman) in 2020. The secondary aim was to assess the effect of a specific batch of normal saline A (batch 132129) compared with another normal saline, B (batches 132589 and 133325), used in the preparation of ^99mTc-DMSA on the abnormal biodistribution of ^99mTc-DMSA. Methods: This was an ambidirectional cohort study that included all patients who underwent ^99mTc-DMSA renal scanning between January and December 2020. Both prospective and retrospective data collection was used. The collected data included possible causes of abnormal biodistribution, quality of ^99mTc-DMSA and normal saline, and time of ^99mTc-DMSA injection. Results: The total incidence of abnormal biodistribution was 26.5%, with the most common cause being a high creatinine level (29%). Normal saline batch A was significantly associated with abnormal biodistribution (49.7%), compared with batch B (6.6%) (P < 0.001). This association was more prominent among patients injected with the ^99mTc-DMSA preparation after 2 h (83.0%) compared with before 2 h (13.3%). Conclusion: A high incidence of abnormal biodistribution of ^99mTc-DMSA was detected and-for what is the first time, to our knowledge, in the literature-a specific preservative-free, normal saline that is up to standard has been identified as a significant cause of abnormal biodistribution. Nuclear medicine professionals and pharmaceutical companies should take note of this possible cause of abnormal ^99mTc-DMSA biodistribution.

Treatment of radiological contamination: a review

After nuclear accidents, people can be contaminated internally via ingestion, inhalation and via intact skin or wounds. The assessment of absorbed, committed doses after internal exposure is based on activity measurement byin vivoorin vitrobioassay. Estimation of dose following internal contamination is dependent on understanding the nature and form of the radionuclide. Direct counting methods that directly measureγ-rays coming from within the body or bioassay methods that measure the amount of radioactive materials in urine or feces are used to estimate the intake, which is required for calculating internal exposure doses. The interpretation of these data in terms of intake and the lifetime committed dose requires knowledge or making assumptions about a number of parameters (time, type of exposure, route of the exposure, physical, biological and chemical characteristics) and their biokinetics inside the body. Radioactive materials incorporated into the body emit radiation within the body. Accumulation in some specific organs may occur depending on the types of radioactive materials. Decorporation therapy is that acceleration of the natural rate of elimination of the contaminant will reduce the amount of radioactivity retained in the body. This article presents an overview of treatment of radiological contamination after internal contamination.

Alkaline degradation of lyophilized DMSA prior to labeling with 99mTc: Identification and development of the degradation pathway by HPLC and MS

INTRODUCTION

Complexes of technetium-99m (99mTc) with meso-dimercaptosuccinic acid (DMSA) have been widely used as diagnostic agents in nuclear medicine. The degradation products (DP) of DMSA formed under different forced conditions have been identified through HPLC-DAD and LC-MSⁿ studies. In this study, the DMSA kit was subjected to forced degradation under hydrolysis conditions as prescribed by the International Conference on Harmonization (ICH) guideline Q1A.

METHODS

Chromatographic separation was accomplished on a reverse phase Shim-Pack VP-ODS (150 mm × 4.6 mm; 5 μm) analytical column using the gradient elution method. LC-MSⁿ analysis was performed using an Esquire 3000 Plus ion trap mass spectrometer, operating under electrospray ionization (ESI).

RESULTS

No products were found under acidic or neutral stress conditions. All the products found were identified through LC-MSⁿ analyses and their fragmentation pathways were proposed. The DMSA standard degraded into an adduct DMSA dimer (2DMSA[-2H+Na]⁺) and adduct DMSA bound to fumaric acid and dithioglucolic acid (DTGA). In the DMSA kit, the degradation products were dimers and trimers of DMSA with tin. A possible degradation pathway is presented.

CONCLUSIONS

This method proved to be convenient and effective since it provided fast and efficient separation of DMSA from its degradation products. The degradation studies carried out were able to delineate the stability of the DMSA standard and the DMSA kit.

Insight into the structure and stability of Tc and Re DMSA complexes: A computational study

Meso-2,3-dimercaptosuccinic acid (DMSA) is used in nuclear medicine as ligand for preparation of diagnostic and therapy radiopharmaceuticals. DMSA has been the subject of numerous investigations during the past three decades and new and significant information of the chemistry and pharmacology of DMSA complexes have emerged. In comparison to other ligands, the structure of some DMSA complexes is unclear up today. The structures and applications of DMSA complexes are strictly dependent on the chemical conditions of their preparation, especially pH and components ratio. A computational study of M-DMSA (M=Tc, Re) complexes has been performed using density functional theory. Different isomers for M(V) and M(III) complexes were studied. The pH influence over ligand structures was taken into account and the solvent effect was evaluated using an implicit solvation model. The fully optimized complex syn-endo Re^(V)-DMSA shows a geometry similar to the X-ray data and was used to validate the methodology. Moreover, new alternative structures for the renal agent ^99mTc^(III)-DMSA were proposed and computationally studied. For two complex structures, a larger stability respect to that proposed in the literature was obtained. Furthermore, Tc^(V)-DMSA complexes are more stable than Tc^(III)-DMSA proposed structures. In general, Re complexes are more stable than the corresponding Tc ones.