EFFECTS OF PRUSSIAN-BLUE AND N-ACETYLCYSTEINE ON THALLIUM TOXICITY INMICE

Background: Thallium poisoning is now rare but still occurs as a resul t of homicide attempts. Prussian blue's efficacy in the treatment of e xperimental thallium poisoning has been demonstrated in animal models, and its use in humans is supported by anecdotal data. Since thallium binds sulfhydryl groups, the use of N-acetylcysteine is also considere d as a potential antidote. Study Objective: To compare the efficacy of Prussian blue and N-acetylcysteine in a murine model of thallium pois oning. Methods: Female Swiss albino mice with free access to food and water were used. Two study doses of thallium, given as a subcutaneous injection of thallium acetate dissolved in sterile water, were chosen: 70 mg/kg (LD(90)) and 85 mg/kg (> LD(100)). A randomized, placebo con trolled study was conducted with survival at 120 h chosen as the outco me measure. Four treatment groups were studied: control, Prussian blue , N-acetylcysteine, and the combination of Prussian blue and N-acetylc ysteine. Prussian blue was dissolved in water and given by oral gavage at a dose of 50 mg/kg, N-acetylcysteine was diluted in normal saline and given as intraperitoneal injections of 200 mg/kg. Sterile water by gavage and normal saline by peritoneal injection were given as contro l treatments whenever an active agent was not given. Survival was reco rded over a 120 h study period and compared at 120 h by a Fisher's exa ct test. Results: At 120 h following subcutaneous injection of thalliu m 70 mg/kg, only 10%, of the control animals survived, Treatment with N-acetylcysteine or Prussian blue increased survival to 35% (p = 0.13) and 50% (p = 0.014), respectively. The addition of N-acetylcysteine t o Prussian blue offered no benefit over Prussian blue therapy alone. C onclusions: Prussian blue was found to decrease mortality from thalliu m poisoning at a dose equal to the LD(90) in this model, but not a dos e greater than the LD(100). No role for N-acetylcysteine in the treatm ent of thallium poisoning was demonstrated by this study.