Purpose: To propose a new and effective dose regimen for stable potassium iodide (KI) repeated prophylaxis in case of prolonged exposure to radioactive iodine.
Methods: The pharmacokinetics of iodine was determined in rats by compartmental analyses after intravenous and oral administrations of the optimal dose of 1 mg/kg KI, which was previously selected in a dose-effect study. The thyroid protection against iodine-125 incorporation was followed during 24 h after a single oral dosing of KI. A repeated KI prophylaxis was modeled using initial estimates of iodine pharmacokinetic parameters.
Results: A dose regimen consisting in administrations of 1 mg/kg daily for 8 days was selected and studied. Plasma iodine concentrations predicted by simulation were verified by experimental data and varied after the third dose of KI between 174 and 1190 μg/l. The inhibition study of iodine-125 binding in the thyroid as a function of the time showed that the protection effect of KI could be correlated to stable iodine plasma concentrations. Hence, a theoretical decrease in iodine-125 thyroid uptake from 63 to 88% could be achieved in a 24 h-interval between two KI doses.
Conclusion: Given the satisfactory levels of thyroid protection, this dose regimen could be envisaged in order to extent KI indications for repeated prophylaxis.
Keywords: dose regimen; pharmacokinetic-pharmacodynamic relationship; pharmacokinetics; potassium iodide prophylaxis; rats.