Comparison of the antidotal efficacy of polyamincarboxylic acids (CDTA and DTPA) with time after acute zinc poisoning

The effect of increasing the time interval between acute zinc exposure and chelation therapy was studied in male Swiss mice. Cyclohexanediaminetetraacetic acid (CDTA), and diethylenetriaminepentaacetic acid (DTPA) were administered ip at 0, 0.25, 0.5, 2, 12, or 24 hr after ip administration of 0.40 mmol/kg of zinc acetate dihydrate. Chelating agents were given at doses equal to 1/3 of their respective LD50 values. Effectiveness of chelation therapy was determined by measuring the ability of the chelators to increase the elimination of zinc and decrease the concentration of the metal in various tissues. Treatment with DTPA or CDTA increased significantly the urinary and fecal excretion of zinc when the chelators were administered at various times following zinc exposure. The greatest antidotal efficacy of the chelating agents was observed at 0.50 hr after zinc injection. Nevertheless, the effectiveness of DTPA and CDTA was decreasing when the chelators were administered later. DTPA was more effective than CDTA in the prevention of acute zinc intoxication. CDTA would be considered as a possible alternative.