Three patients, in 1971, were the first to receive Prussian blue as a treatment for thallium poisoning.15 Although daily fecal thallium concentrations were not determined in two of the three patients because of severe constipation, an approximately sevenfold increase in fecal thallium elimination over baseline was attributed to Prussian blue therapy in the third patient. Subsequently, many humans with thallium poisoning have received Prussian blue, with or without a cathartic, as part of their therapy.1,3,5,6,10,15,38,41,49,53,54,58 Unfortunately, other components of therapy that may have confounded the effects of Prussian blue in these cases include single- or multiple-dose activated charcoal, and the use of D-penicillamine, dimercaprol, ethylenediaminetetraacetic acid (EDTA), succimer, 2,3-dimercaptopropane-1-sulphate (DMPS), forced potassiumdiuresis, and either hemodialysis or hemoperfusion. There are no controlled trials of any of these modalities alone or in combination, and most of the data presented are based on single case reports or small case series.
One of the largest series was composed of 11 thallium-poisoned patients who were treated with soluble Prussian blue.49 This report not only demonstrated the tolerability of Prussian blue, but also was the first to systematically evaluate its fecal elimination. In all individuals studied, fecal elimination remained high, even when urinary elimination fell, suggesting selective redistribution of thallium into the gut.49 Although the authors commented on clinical improvement in these patients, the lack of controlled data makes these subjective observations difficult to interpret. Similarly, a substantial reduction in thallium half-life was demonstrated when Prussian blue was compared with no therapy at all in patients with thallium poisoning.6