Evaluation of Potassium Iodide (KI) and Ammonium Perchlorate (NH₄ClO₄) to Ameliorate ¹³¹I^- Exposure in the Rat

Abstract

Nuclear reactor accidents and the threat of nuclear terrorism have heightened the concern for adverse health risks associated with radiation poisoning. Potassium iodide (KI) is the only pharmaceutical intervention that is currently approved by the Food and Drug Administration for treating ¹³¹I^- exposure, a common radioactive fission product. Though effective, KI administration needs to occur prior to or as soon as possible (within a few hours) after radioactive exposure to maximize the radioprotective benefits of KI. During the Chernobyl nuclear reactor accident, KI was not administered soon enough after radiation poisoning occurred to thousands of people. The delay in administration of KI resulted in an increased incidence of childhood thyroid cancer. Perchlorate (ClO₄^-) was suggested as another pharmaceutical radioprotectant for ¹³¹I^- poisoning because of its ability to block thyroidal uptake of iodide and discharge free iodide from the thyroid gland. The objective of this study was to compare the ability of KI and ammonium perchlorate to reduce thyroid gland exposure to radioactive iodide (¹³¹I^-). Rats were dosed with ¹³¹I^- tracer and 0.5 and 3 h later dosed orally with 30 mg/kg of either ammonium perchlorate or KI. Compared to controls, both anion treatments reduced thyroid gland exposure to ¹³¹I^- equally, with a reduction ranging from 65 to 77%. Ammonium perchlorate was more effective than stable iodide for whole-body radioprotectant effectiveness. KI-treated animals excreted only 30% of the ¹³¹I^- in urine after 15 h, compared to 47% in ammonium perchlorate-treated rats. Taken together, data suggest that KI and ammonium perchlorate are both able to reduce thyroid gland exposure to ¹³¹I^- up to 3 h after exposure to ¹³¹I^-. Ammonium perchlorate may offer an advantage over KI because of its ability to clear ¹³¹I^- from the body.

Acknowledgements

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.

Current address for D. C. Ferguson is Department of Veterinary Biosciences, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.