Bioavailability of iron and cyanide from oral potassium ferric hexacyanoferrate(II) in humans

After oral administration of 500 mg KFe[Fe(CN)₆] labelled with⁵⁹Fe either in the ferric or ferrous position and with¹⁴C in the cyanide group only 0.22% of the Fe^II and <0.04% of the Fe^III were absorbed in three male volunteers. Only 2 mg non-complex bound relabelled cyanide (0.03 mg CN-/kg body wt) were absorbed from 500 mg [¹⁴C]KFeHCF, which is about a factor of 20–100 below the lethal dose in humans (0.5–3.5 mg CN-/kg body wt). Therefore, iron(III) hexacyanoferrates(II) can be considered as safe antidotes, i.e. for inhibiting the intestinal absorption of radiocaesium or for accelerating the excretion of already absorbed^134/137Cs in the case of a severe nuclear accident.