The results of a chelation study using Ca-/Zn-DTPA to treat 25 patients diagnosed with Gadolinium Deposition Disease (GDD) will be published in the June 2018 issue of Investigative Radiology.  The complete article is not freely available to the public.  However, you can find the abstract of, “Intravenous Calcium-/Zinc-Diethylene Triamine Penta-Acetic Acid in Patients with Presumed Gadolinium Deposition Disease – A Preliminary Report on 25 Patients”, by Semelka et al. at https://www.ncbi.nlm.nih.gov/pubmed/29419708

According to the FDA, Calcium-DTPA (Ca-DTPA) and Zinc-DTPA (Zn-DTPA) are drug products that have been used for over 40 years to speed up excretion of the actinide elements plutonium, americium, and curium from the body.  Gadolinium (Gd) is a lanthanide series element that shares a number of chemical properties with actinides.  The purpose of the study was to determine if the FDA-approved actinide metal decorporation agents Ca-/Zn-DTPA could be beneficial for symptomatic patients with GDD who had retained gadolinium from the gadolinium-based contrast agents (GBCAs) that had been administered for their MRIs.  

The chelation study consisted of 18 women and 7 men who had received at least one administration of a gadolinium-based contrast agent.  The study called for 3 treatment sessions.  Each treatment session consisted of the intravenous administration of Ca-DTPA followed 24 hours later by Zn-DTPA.  Of the 25 participants, 15 had treatments 1 month apart, and 10 with treatments spaced one week apart.  Seven people did not complete the study for various reasons.

The results of the chelation study are mixed.  While the amount of gadolinium excreted in urine increased in both the monthly and weekly treatment patients, symptoms did not improve as much.  In their summary, the authors said, “The results are very positive regarding the physical removal of the metal.  The symptomatic improvement after 3 sessions of rechelation was not as consistently positive and was also more modest in nature.  This likely reflects that more than 3 chelation sessions are necessary”.

While the study shows that Ca-/Zn-DTPA are safe and effective at removing gadolinium, the results indicate that 3 treatment sessions are not enough to bring about significant improvement in GDD patients’ symptoms.

Full disclosure –

I participated in the DTPA chelation study.  I did 8 two-day treatment sessions in 2016.  I experienced a temporary “flare-up” reaction of some symptoms which participants were told might occur.  My flare-ups did not happen after each session and they usually only lasted a few days.  I was one of the people who did not have much improvement in their symptoms.  However, I understand that chelation therapy is most effective when it is started soon after exposure to a toxic metal like gadolinium.  In my case, it had been 6 years since my last of 5 doses of a gadolinium-based contrast agent.  I expect that it would take considerably more than 3 treatment sessions to remove much of the gadolinium that is still in my body.  However, even 6 years after my last MRI, I excreted considerably more gadolinium after my treatments as confirmed by the urine testing that was performed before and after each treatment.

Ca-/Zn-/DTPA are FDA-approved but not specifically for chelation therapy to remove gadolinium.  Hopefully the FDA will approve the drugs for the treatment of patients with GDD so that DTPA becomes widely available to people who want to do chelation therapy.  Currently, many GDD patients are being treated with EDTA.  However, it appears that based on stability constants, DTPA should bind much more tightly to Gd than EDTA does. That should result in less gadolinium being dropped and redistributed in the patient’s body.  I believe that is reason enough for the FDA to approve Ca-DTPA and Zn-DTPA for the treatment of patients who have retained gadolinium from gadolinium-based contrast agents administered for contrast-enhanced MRIs.

Sharon Williams
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Semelka, R. C., Ramalho, M., Jay, M., Hickey, L., & Hickey, J. (2018). Intravenous Calcium-/Zinc-Diethylene Triamine Penta-Acetic Acid in Patients with Presumed Gadolinium Deposition Disease: A Preliminary Report on 25 Patients. Invest Radiol, 53(6), 373–379. http://doi.org/doi: 10.1097/RLI.0000000000000453

U.S. Food & Drug Administration; Bioterrorism and Drug Preparedness. (2015). Questions and Answers on Calcium-DTPA and Zinc-DTPA (Updated). https://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm130314.htm

U.S. Food & Drug Administration. Product Labeling Calcium-DTPA (2013). Reference ID: 3279941. https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/021749s008lbl.pdf

U.S. Food & Drug Administration. Product Labeling Zinc-DTPA. (2013). Reference ID: 3279944. https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/021751s008lbl.pdf

Table of Stability Constants

Click to access Chelate_Table_of_Stability_Constants.pdf