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Biological Effects and Medical Treatment
Published in Alan Perkins, Life and Death Rays, 2021
If the patient has been exposed to radioactive iodine such as iodine-131, a thyroid-blocking agent should be given to reduce the internal uptake of radioiodine in the thyroid gland. Potassium iodide is the drug of choice and should be administered within a few hours to be effective. If a metal radioactive poison has entered the circulation, it may be possible to give an agent to bind the metal and increase the speed of elimination from the body. The more quickly a radioactive poison is removed, the lower the radiation dose and the less serious the health effects will be. Prussian blue (ferric hexacyanoferrate) will increase the elimination of caesium and thallium radionuclides from the bowels. This has been used to treat casualties in the past and is considered to be a good standby in possible terrorist incidents using stolen or abandoned radiation therapy sources or industrial sources containing caesium-137. Chelating agents are also used as scavengers of radiometals and are most effective when they are given shortly after radioactive materials or poisons have entered the body. During the Second World War, dimercaprol, an organic dithiol compound, was developed as an experimental antidote against the arsenic-based poison gas lewisite. After the Second World War, lead poisoning became a major problem in naval personnel as a result of their jobs of repainting the hulls of ships. The medical use of a salt of ethylene diamine tetra-acetate (EDTA) known as sodium calcium edetate was introduced as a therapeutic chelating agent to treat lead poisoning. In the 1960s a further compound meso-2,3-dimercaptosuccinic acid (DMSA), a related dithiol with far fewer side effects, was introduced. A further chelating agent diethylenetriaminepentaacetate (DTPA) was introduced and found to be a more powerful metal sequestering agent. DTPA comes in two forms: calcium (Ca-DTPA) and zinc (Zn-DTPA). In 2004 the US Food and Drug Administration determined zinc-DTPA and calcium-DTPA to be safe and effective for the treatment of internal poisoning with plutonium, americium or curium. When given within the first day after internal contamination has occurred, calcium-DTPA is about 10 times more effective than zinc-DTPA, but after 24 hours have passed, calcium-DTPA and zinc-DTPA are equally effective in chelating these radioactive materials.1
Fatal lead encephalopathy following the ingestion of fishing weights (“sinkers”)
Published in Clinical Toxicology, 2022
Allister Vale, Nicola Barlow, Sally Bradberry
Further investigations on samples obtained during admission showed prominent basophilic stippling and a blood lead concentration of 350 µg/dL. Some four weeks after the first admission, when the blood lead concentration was 571 µg/dL, he agreed to be readmitted. He was confused and agitated. He was transferred to the West Midlands Poisons Unit for chelation therapy. On arrival, his diction was difficult to understand, and he was unable to move any muscle below his head. A full neurological examination could not, therefore, be performed. The blood lead concentration on arrival at the Poisons Unit was 630 µg/dL. He was commenced immediately on intravenous sodium calcium edetate 75 mg/kg daily. He received two courses before his condition deteriorated further. He died from lead encephalopathy 58 h after admission. The blood leads concentrations 24 h and 48 h after admission were 531 µg/dL and 380 µg/dL respectively. During the first and second 24 h of chelation 56,552 µg and 34,290 µg of lead were excreted in the urine respectively.
Gadolinium-based contrast agents – what is the evidence for ‘gadolinium deposition disease’ and the use of chelation therapy?
Published in Clinical Toxicology, 2020
Kerry A. Layne, David M. Wood, Paul I. Dargan
The second paper [41] reported a patient who was treated for zinc toxicity who had undergone two gadolinium-based contrast agent-enhanced MRI scans and was incidentally noted to have increased urine gadolinium excretion. His chelation therapy consisted of a regimen of 3–5 capsules per day of a dietary supplement that contained (per capsule) sodium calcium edetate 75 mg and succimer 25 mg, followed by 22 intravenous chelation infusions with edetate disodium or sodium calcium edetate 1500–3000 mg per infusion.