Pahuja D N, Rajan M G, Borkar A V, Samuel A M
Radiation Medicine Centre, B. A. R. C., Parel, Bombay.
Health Phys. 1993 Nov;65(5):545-9. doi: 10.1097/00004032-199311000-00014.
Potassium iodide is the preferred thyroid blocker for personnel handling radioiodine and is recommended as a prophylaxis for the population in the near-field of a nuclear reactor which would be likely to be exposed to radioiodine in an accidental breach of containment. However, in hot and humid climates, this hygroscopic chemical has a poor shelf life due to hydrolytic loss of iodine vapors. On the other hand, another iodine-rich salt, potassium iodate (KIO3), is quite stable and has a much longer shelf life. The present study compares potassium iodide and KIO3 as thyroid blockers and examines the appropriate time at which they should be administered in case of radioiodine exposure. Either of the two were given in recommended dosage (100 mg stable iodine per 70 kg body weight) at -2, 0, +2, +4, +6, and +8 h after administration of tracer quantities of radioiodine (131I) to age-, weight-, and sex-matched rats. 131I uptake in thyroid was measured 24 h after its administration in the experimental animals and compared with placebo administered controls. Results suggest that KIO3 is as effective a thyroid blocking agent as potassium iodide. In comparison to controls, 24-h thyroid uptake of 131I can be substantially reduced if potassium iodide or KIO3 is given to the animals within 2-4 h after exposure to 131I. Another noteworthy observation is that KIO3 is effective even at 8 h when administered at twice the usual dosage in comparison to the single dose, which does not show appreciable thyroid blocking properties after 8 h.
碘化钾是处理放射性碘人员的首选甲状腺阻滞剂，对于可能在核反应堆安全壳意外破裂中暴露于放射性碘的近场人群，也推荐将其用作预防药物。然而，在炎热潮湿的气候条件下，这种具有吸湿性的化学品由于碘蒸气的水解损失，保质期较短。另一方面，另一种富含碘的盐——碘酸钾（KIO₃）则相当稳定，保质期长得多。本研究比较了碘化钾和碘酸钾作为甲状腺阻滞剂的效果，并探讨了在放射性碘暴露情况下它们的最佳给药时间。在给年龄、体重和性别匹配的大鼠注射示踪量的放射性碘（¹³¹I）后，分别在 -2、0、+2、+4、+6 和 +8 小时以推荐剂量（每 70 千克体重 100 毫克稳定碘）给予这两种药物中的任何一种。在实验动物注射¹³¹I 24 小时后测量甲状腺对¹³¹I 的摄取量，并与给予安慰剂的对照组进行比较。结果表明，碘酸钾作为甲状腺阻滞剂的效果与碘化钾相当。与对照组相比，如果在暴露于¹³¹I 后 2 - 4 小时内给动物注射碘化钾或碘酸钾，¹³¹I 的 24 小时甲状腺摄取量可大幅降低。另一个值得注意的观察结果是，与单次给药相比，碘酸钾在 8 小时时以两倍常规剂量给药仍然有效，而单次给药在 8 小时后则没有明显的甲状腺阻滞特性。
