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

After oral administration of 500 mg KFe[Fe(CN)6] labelled with 59Fe either in the ferric or ferrous position and with 14C in the cyanide group only 0.22% of the FeII and less than 0.04% of the FeIII were absorbed in three male volunteers. Only 2 mg non-complex bound 14C-labelled 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.